When to replace PSU?

[4GHZ_or_bust]

Is there a guideline or general idea for replacing PSU that isn't failing but has been in use almost 24/7 for about 18 months or so? I'm using Ultra brand 600 watts (http://www.ultraproducts.com/product_details.php?cPath=52&pPath=510&productID=512) and the 5v and 12v are less than 0.05v off spec by my meter. The only limitation is it's not SLi capable, only 35A on 12v rail, and only 1 PCI-e power connector with this PSU. I don't have any plan to get second video card this year though.

I don't want to keep using a well used PSU until it goes up in smoke and take my PC down with it.

[ou_phidelt]

Just keep an eye on the rails and you will be fine. As long as the temps have been in line I wouldn't worry about much yet. I am not fond of that brand and wouldn't go much beyond 3 years. What kind of load do you put on it, 24/7 cruncher? Have you measured the power draw to get an idea of the % load you are putting it under?

[4GHZ_or_bust]

I don't have any means of measuring power without unplugging and using my meter inline but based on web site power supply estimator I'm probably doing 400 watts so I have fair amount of head room.