@Kimmi81 Those demographics seem fine, nothing that the game can't handle. How does RAM use behave as you play? It would be helpful to know whether you get a steady climb as you play, or sudden spikes, or there's no sign at all that Sims 3 is getting close to the memory limit before the crash. To test, play in windowed mode and position the relevant value in the Task Manager where you can see it behind the game window, and glance at it every few minutes to see how it behaves.
I would also suggest running an MC town reset (MC > Town Options > Reset Everything) to see whether it helps. You can exclude the current lot, under MC Settings, if you don't want your own sim reset, and running the reset in the middle of the night should be minimally disruptive.
If that doesn't help, please list the mods you currently have installed.