The PS3 is more simple in the way the layout of things are. With the Xbox, in order to gain access to the innards, the plastic top and bottom pieces have to be pried off of their clips and hope they don't break, then the side pieces unscrewed, then finally the shield can be unscrewed and access to the innards gained. With the PS3, it's one security screw for the top piece, then the eight long screws, you're inside and things are easily removed from there. A full Xbox thermal paste reapplication, about an hour if not doing the x-clamp fix. Two hours if so. A full PS3 thermal paste reapplication, no more than 30 minutes.
If you don't feel very hot air blowing out the back at idle and it's just warm, you should be good for awhile. In general, I don't rely on thermal paste that's been laying around for more than 6 months. Of course, when I used to repair laptops, the thermal paste would constantly be used up.

The good news is it's very easy and quick to get back to that spot to reapply.
If anyone might be interested, I'm probably going to have three or four used fat PS3's for sale soon here. Just the PS3. Will probably sell them for $140-$150 depending on model and what I had to do to fix it. I'll probably leave the firmware alone on each one or only update to 3.41. The newest update from a few days ago is causing hard drive upgrade issues for people. I'm still putting them through testing during what little free time I have to ensure all is well.
Thanks! The PS3 is pretty much just disc drive, power supply, motherboard, heat sink, fan, hdd, memory card board, power/eject board. I've never seen inside of a X360. Is the PS3 that much more simple?
I used Acrtic Ceramique, I think AS5 wasn't in stock at Newegg when I built my last system three years ago. Considering the paste I used has been sitting for a few years, should I get a fresh tube of AS5 and apply it while my PS3 is unbuttoned or just roll with things now until it dies again?