Do you run your games off the hard drive? If not, you should. It would minimize wear on your disk drive.
The PS3's blu-ray drive isn't exactly that reliable either (in fact blu-ray drives crapping out are the most common problem with PS3s. Not YLOD) so don't think the slim is gonna be the solution. At least you have the option for RRoDing your console and getting it replaced within that 3 year span. If you ditch the 360 (along with the extensive library you built up), get a PS3, the blu-ray drive craps out (or you get YLOD or whatever) after the short warranty period, then what?