Hiya there, I was gonna buy this psu (the OCZ ModXStream) however when I discussed it with my friend he said that it was around 2/3 years old and that I should buy the OCZ ZT Series which is much newer, when I went through the technical specs and reviews there wasn't much difference except the ModXStream had better reviews (from around 2 years ago), and I came to ask before buying one, does the age of the PSU really matter that much and change the performance?
If you are running a high performance enthusiast level machine it would make a difference, I'm talking dual or triple gpus etc, otherwise there is nothing wrong with running a 2/3 year old psu as long as it meets your machines component power specifications without an issue. If your 3 year old psu was of good value, and not a cheapy like some sell, you are likely fine.
If it is still new there will be no difference.
If it has been running for 3 years,YES there will be a difference.
Capacitors AGE, meaning the slowly lose their performance over time when used.
A 5 year old 500 watt powersupply is good for about 425 watts, depending on the quality of the capacitors. Cheap capacitors=less, quality capacitors=more.
OCZ does not manufacture power supplies, they relable other manufacturers power supplys.
Check this link and see if the exact model you are looking at is a tier 3 or higher unit, some OCZ models are not good units. http://www.eggxpert.com/forums/thread/323050.aspx
As others have said, psu's do indeed degrade over time. The capactiors degrade over time resulting in fluctuations in voltages, and eventually something frying inside the psu.
But however, a well built PSU can give many years of of service when it is designed well and uses good components.
A supply with a crappy design but with good components can also lead a short life. This is mainly because of poor voltage control design which can cause the same effects of bad capacitors.
Also, some people are confusing design life versus component life.
How long a model has been in production means nothing.
This is the answer to your question.
Certainly, newer, different designs out there, but it's not like buying a car or something, the basic design of PSU's have been virtually unchanged for decades now. What you are looking for is features. Like good under/over voltage control for example. Some cheap manufactures go for under voltage control instead of over voltage, and instead rely on a cheap fuse to control the over voltage. You want a PSU that has the ability to electronically control the over/under voltage, AND still have the fuse there as a failsafe.
In the end, you are gonna have to do the research your own PSU, and go with what you can afford.