SPCR

If I keep my power supply inside my case completely (due to a modded reverse-ATX case, for which it's best to keep the PSU inside completely at the bottom of the case... somewhat near the CPU, which actually runs at sub 52C at all times, usually more like mid 40s for gaming, but I"m taking into consideration a graphics card that's going to help with heating up the case), I think it's going to get intake temperatures of around 45C, periodically higher - is that going to seriously affect its lifespan? It is a good quality PSU (PC Power & Cooling MKII 750 Watt) and normally runs very cool. Is it a terrible idea to keep the power supply without fresh air intake like that, or is it going to be okay for the next couple years at least (at which point I'll be getting a new PSU anyway)?

Actually, I think I'm wrong. I think the large fan is actually an intake fan, and the air is exhausted through the mesh toward the CPU cooler (which is fine -- the CPU runs at cool temperatures anyway). I just got confused because when I was putting my hand over the fan, it was blowing air toward it, but I think it's due to some of the air getting sent backwards, as it happens with some fans (like my Gentle Typhoons on a radiator). In this case, I have a 140mm intake fan not too far, so I think the PSU should be okay.