How long my system will last?( guestimate )

Hardware will last as long as the hardware itself does not fail.

You might want to re-phrase your question. I'm guessing you're more wondering how long your system will last in the context of how well it will run the applications and play the games you play. If so, the system will last as long as you perceive it to be operating fast enough and as long as it runs the apps and plays your games at a level you find acceptable.

That's the beauty of building your own machine, you can upgrade the individual parts to extend the life of the machine, i.e.; add more RAM, upgrade cpu, upgrade video card, etc...

I used this system for almost 3 years for playing games

AMD 4400+, 2gb ddr dc, asus premium sli mobo, evga 7800gt

I only recently upgraded to a x9450 quad, 4gb ddr2 dc, asus xfire x48 board, and a 4870. I am hoping this will last me as long

Yours will last as long as you can do what you want with it, when it starts to bog then you will probably start to check out new parts.

My guesstimate:
The system will function for 10-20 years.
You will want to replace it in 2-3 years.

IIRC they claim about 1% failure in after 10 years at stock speeds and voltages with adequate cooling. I wouldn't doubt that as I have used CPUs that were at least that old that ran perfectly fine.

Maybe, maybe not. I am edging on the side of "not" as that's significantly out of spec and drawing >2x the power of a stock chip. It might last a year or two at that voltage and speed, but I'd put decent odds on it being dead 5 years from now due to electromigration.

MU_Engineer every time you make a post I learn or have an oppurtunity to learn something. Reading this thread I was wondering if it was the heat or the electical charge that actually effected the silicon but now I know, thanks. So no need to explain electromigration, I found it on Wiki:

http://en.wikipedia.org/wiki/Electromigration

Eeerm there's another thread discussing a low power usage file server and a certain poster mentioned the idea of a standalone photovoltaic unit possibly powering the unit 24/7 with battery bank of course. But we need someone with an engineering background to work out exactly whats needed.

Personally I wouldn't worry about your situation at all. If you look at the system clocks and cpu clocks in competitions around the world they are VERY high, with many chips overvolted well beyond manufacturers recomendations. Also when you read about cpu's overclocked to the point of failure, they rarely ruin other components even when they do die. I remember reading about alot of blown moffsets on the X38 boards at sub zero but they claim this has been rectified on the X48 sets. Remember that's at sub zero, well beyond general air and water cooling.

Also if your Q6600 does die prematurely have a think about what it will cost to replace in 1 or 2 years, even if it was available then. It would be DIRT cheap. So all things considered, don't worry. Just remember when your overclocking if you overvolt something a little more than you comfortable with and your system doesn't reach stabilty, don't keep overvolting because more than likely your problem is somewhere else.