If I can play games at "medium" settings and have no lag than I am good. When my system is unable to play games at medium settings it is time for a upgrade.

My current/future financial situation.

Other than been able to play games at a normal or decent resolution....Having The Money To Upgrade....:')

First!

Whether I really and truly want to play a game well. At the moment, nothing intrigues me and I can play 90% of what I play at or close to max settings. Since there havent been any major releases recently that i wanted, Its been awhile. Also not having money puts a damper on that sort of thing. Currently waiting for DX11 cards.

New Windows OS and old hardware >3 years old, i.e. for me this october (earliest). Have pentium 4 3.2 GHz and Radeon 800 series. Getting i7 and a DX11 graphics card below 200$, 12GB Ram (at least). No new drives or monitors.

2 -> 3 year cycle

Money, but in terms of when I "need" to upgrade: Full system every 4 years or so, or an upgrade every other year if I don't need a complete system overhaul to do the upgrade.

If there is a great game that can be made better with better gear.. then I will upgrade. I think the next revolution for PC gaming will occur 2010 or 2011.

I usually build a system and its total life is usually about two years. After the first year, i will usually do a GPU and harddrive upgrade. A year later I usually build a new system and repeat the cycle.

I only do the GPU upgrade if a new architecture has been released, or if I am adding a second card.

In the past, it was compatibility with new functionality and an element of speed.
But for the 1st time in a long time, I am truly satisfied with my desktop computing experience. Quad core, 2+ Ghz, 8GB of RAM (4.5 of which is rarely used) Raptor Raid 0 array, connectivity, the ability to use any application I throw at it and get it to run in a timely fashion, from encoding videos to running web-apps... It can all be done and done with little to no lag. With the new OSs I get more functionality out of my TV tuner and have turned my system into a multimedia station. Plenty of screen real estate (2x22" LCD's). I am golden. Thousands of gigabytes of information available... My biggest upgrades involve increasing my storage space (and redundancy).

Now all that holds me back is my mobile computing experience. Even with the upgrade to SSD, and it was a great kick in the pants to my tablet, I still don't use it as a proper extension of myself as far as scheduling and communication. It is just too bulky, and the processor, weight, and short battery life hold it back.

iPhone is getting close to what I am looking for, and my (extremely) preliminary experience with the G1 is promising, but the data plans hold the whole thing back, and as with any 1st generation device, I question its longevity...

So in short, when they find a way to make the snappiness of my desktop right now fit into a tablet that weighs less than 2 lbs, with a battery life that exceeds 10 hours for a reasonable price, and when they come out with a phone that has the features I want with a plan I want, my upgrade cycle will effectively be limited to when I get popped capacitors.

After a significant price drop on the parts I want to upgrade.

I have a tendency to buy my GPU a little early instead of waiting for price drops . Other than that I'm 'usually' patient. Complete overhaul only when I need a new CPU socket.

1 year cycle or so. I upgrade whenever I have the money, find good enough deals, or can't play games I want to.

QFT

When $150 can get me a CPU that performs 2x faster. (by then, mobo and ram of a new platform has gone down as well.) My upgrade history has been Athlon 1.0 Ghz, Pentium 4 2.8 Ghz, Core 2 Duo 3.0 Ghz.

When something breaks or I can no longer play a game at decent settings at a respectable frame rate. Usually every two or three years I have a real big upgrade and every two "cycles" I'll change cases.

When something significant breaks or my PC cannot do well something (eg, a game) that I want it to do well.

That approach is bad enough lol, and anything more is certainly a waste of time and money.

In the past I have upgraded when I found new hardware that I really wanted. More recently my hardware has been fast enough so I didn't feel any reason to upgrade. I just replaced my 7 year old home desktop, because it got too slow for me. I had upgraded its hard drives and OS about 3 years ago. Earlier this spring I built an entirely new desktop and gave away the old one.

At work I got a new CAD workstation 8 years ago. We replaced it after 4 years with a new workstation, but the old one was performing fine. After 3 years the replacement was very slow, so I replaced it recently. Unfortunately software demands increase as fast as hardware speed and force upgrades. Eight years ago my AMD single core machine running Win98SE and AutoCAD 2000 was as productive as my current 3.8GHz core2 machine with WinXP and AutoCAD 2009. The new computer is approx. 8 times as fast as the original one, the new software is 8 times as slow as the old software. No net gain.

Based on lost productivity at work, I think I should replace my workstation at less than 3 years of age, but my home computer should last 4 years or more.

Lastly, I have a 5 year old laptop that I use for travel. It still works fine, but I needed to run some of our CAD apps so I bought a new laptop recently with P9500 processor. Right now I alternate between the 2 laptops but eventually will phase out the old one.

The fps of the games i'm currently playing determines my upgrades.I used to get a new video card every year,but since the 880gtx i've been getting 2 years out of them lately.

Generally, a thousand dollar system will last me a year; maybe more depending on how great the hardware was when I bought it. Systems that I'm thinking about are the geforce 4 and 8; cards that really could survive for years if you bought at least the mid-range card.

games mainly determan when i get a new PC if there aren't any more upgrade paths for my current PC or it would just be cheaper to build from the ground up thats what i do if i start lagin in games at medium settings then its time for another upgrade!

When the hardware I wan't to put in no longer fits in. Eg. Last upgrade was from my old PC to one that had PCI-E.

Gettin a real job would definitely determine my upgrade cycle.

That's about it for me too, although rarely does anything significant break, as I only do mild OC and try to buy quality parts. I'll get a new GPU if I think I'll benefit from it now and in the immediate future. The HD4850 I got 5-6 months ago is still more than my current games/apps need, and may be for some time.
I also have gotten to upgrade by passing my current machine on to a family member (e.g. my father got my last one), but there's no one left in my family who needs a PC, particularly not a Q9450.

I upgrade when I need more awesome in games.
I never just buy a whole new box.
I last "upgraded" cause my computer broke, sadly with PC gaming the way it is at the moment (full of crappy console ports) there has been little reason for me to upgrade to play the latest games

I think its really sad whats happening to PC gaming, the PC has always been the people's system, consoles are the corporations' systems (also Macs and Laptops on the hardware side).

full upgrade when your motherboard can't grow anymore. Chances are i will use my e6750 until it becomes a bottleneck...hopefully by that time the core i5 and i7 are down to 200 dollars and 100 bucks for a motherboard...so i can make that upgrade....ddr3 would have to come way down too. i guess for me it has to be serious bang for the buck and actually needed. right now my system does all i need at full settings.

money... how much i have vs how much it costs to upgrade is the most important factor for me. I will not upgrade if i cant afford it, and if i can, i have to get value for my money. It always comes around to about a 3 to 4 year cycle where money is good enough to upgrade and value for technology is right where I can afford it (best components for the price).

Every two years.

True. I'm planning to build a completely new gaming system in the next 4 years or so (after TES 5 comes out, Modern Warfare 2, etc.)

I tried jumping into the console gaming... needless to say I will never go back. Too much "DRM" and restrictions. Give me a PC any day.

Once my computer seems noticeably slow compared to a 'normal' prebuilt (and overclocking doesn't help the situation) a chain of events usually leads to me breaking down and doing an upgrade.