The flame bait...
As James said, what games are you playing and on what model OP?
Some games freezes allot, like Fallout 3 and Fallout New Vegas, This is one of the reasons Bethesda changed the game engine for their games (Elder Scrolls: Skyrim), my point is, see if it does on specific games or any game, are you getting error messages or is it just freezing as if a screen shot on a PC is taken?
But if you’re not playing a game that’s not known to freeze, maybe it’s an issue with the PS3 its self, is it well ventilated? Are its vents free from dust? Etc.