I have played dozens of PS3 games, and keep my machines and discs in immaculate condition, unsoiled and well ventilated. Fallout 3, Fallout 3 GOTYE and Fallout: New Vegas are the only games I've had crash and require a hard reboot. And they do it consistently with New Vegas being easily the worst. Oblivion never totally crashed on me, but it chopped and lagged like nobody's business. I love these games, but this is not a coincidence.
/this for sure.
Unfortunately the memory cache problem with this game is the same for all the Havok engine powered games and won't be corrected by Bethesda/Obsidian. They can't. They tried to limit the problem by making FLNV much smaller in regards to loaded cache, but it didn't get rid of the cumulative problem. Even though there are no large fights or areas in FLNV and even though they cut the Strip into three sections, it still adds up if you move around.
Reset your game often, even restart the ps3, no less than once an hour. I usually restart the game every thirty minutes or so when I make a new clean save. I move around quite a bit, dropping stuff off at Goodsprings and making a caravan cards run to Nash, Chet and the Outpost, so my cache builds up quick. I notice performance issues after about 45 minutes of my style of play, so 30 minute save and reset works pretty good. Still lock up every once in a while. bleh.