Sims 2 has always had a random crashing issue with no errors, since 2004. It will crash usually around the 1 hour mark. If you are lucky, it will be longer or it won't happen that play session. I've had days where I accidentally left the game running and came back hours later to find it still running and days where it crashed on me more than once. Whatever causes it, they never solved it. The prevailing theory seems to be that it has something to do with how the game accesses or uses ram.
My advice is first, to save frequently. I save any time I do anything of importance and probably every few minutes in general. Thankfully Sims 2 saves quickly. When you hit the 1 hour mark, save and quit the game. Go into the game file and delete all of the cache files, then start the game again.
