I myself dust out my computer every month, no overheating. However, Morrowind and Oblivion as well as FO3 do get more unstable the more you play. I always make fresh saves and keep no more than 20 saves at most but still get crashes. There has to be some kind of save game "cleaner" or defragmenter or something that bethesda can produce.
Yeah you'd think so, but I'm guessing it is a limitation somewhere in the game engine that they know they can't fix. Hopefully Fallout 4 will use a completely new engine desgined from scratch. To be fair though, once you are aware of the issues with these games (I've played Oblivion, FO3 and NV) it is relatively easy to avoid. The rest is down to sheer dumb luck as to whether the game likes your PC or not.
I just swapped out my old 8800GT for a GTX 260 and I've had only one crash in around 20 hours of gameplay. Same drivers and same basic GPU architecture. Even the same type of memory. Only difference is in raw power. And yet, crashing reduced by 200%. Go figure. I guess I am willing to accept the problems with the games because I love them so much.
When I play Mass Effect, however, the few major problems I have make me angry beyond reason. I guess I just love Fallout so much that I accept her flaws. Much like my wife