I just spent a pretty good amount of money on a PSU and want it to last a long time, usually I unplug my computer at night so no one trips on the cord. Someone told me it's also good for the PSU to do this because it lets the caps power down, and someone told me it was bad to let the caps constantly lose and regain their charge. What do you guys think?
I run my PC's 24/7 365. I always HAVE done that though through a little over a decade of building my own systems and I haven't ever had an issue. The only times my PSU's have given me problems is when they were VERY low quality and blew under stress.
My personal feeling here (which is based on stuff told to me by my guru 20+ yrs ago plus some that I've gleened since) is current desktop PSU's are designed for 24hr use. I do not believe that it is good practice to power down the caps on a PSU. By design actually, when the average PC is shut down, the PSU still recieves power (very few people are like yourself, unplugging the PSU) as does the motherboard.
Personally, like most of the above, I also run 24/7.