I have had Error 12 once, in nearly 10 years. Because I played so long without saving. I never experience it, and I always thought it was because I save often, always use Save As and I restart my game every couple of hours.
When I stop getting the Sims 3 spinning cursor, and I see the Win 7 circle in my game instead, I know then that it is time to turn my game off, wait a little and the restart it.
I haven't always played on the decent PC I have now. I used to have a fairly low end dual core and only 4 gigs of Ram, but I tweaked what I could, and tried to take care of my game. I didn't use too much CC, I didn't run it for too long, and I didn't try to run it on highest settings and force my PC to perform far beyond its capabilities.
I have a much better PC now, but all that still sticks. This could all be just voodoo on my part, but it's worked for me so far and I've never had problems.