@cloudygreyskies It's possible that the card is still overheating, just not as quickly, and so the crashes happen later. You can run another hwinfo log and upload it if you want, and I'll take a look to confirm.
It may be though that your card isn't capable of cooling itself properly anymore. This might be fixable, if there's something mechanically wrong with the fan. It would also probably help to take it apart and reapply thermal paste: given the age of the card, the original thermal paste is probably totally dried out by now and not nearly as effective as it was. If this isn't something you're comfortable doing yourself, you could ask a friend, or call computer shops in your area and get an estimate.
Beyond that though, given the age of the card, it might not be worth investing a lot of money in fixing it. Aside from applying thermal paste, you could help the card run better by lowering the graphics settings and manually limiting in-game framerates. Those steps would lower the workload for the GPU, although how much that would help would depend on the settings you currently use and the fps you're already seeing—if you're playing on low and getting low framerates, there's not really any room for improvement.
If you'd like to see your in-game framerates, bring up the cheats console (crtl-shift-c) and enter "fps on" without quotes. A number will appear in the upper right corner of yoru screen. Normally you'd want to see 60 or close to it (the refresh rate of your monitor is 60 Hz), but you could manually limit it to 30 and still get what most people think is a playable experience. Let me know what you're getting now, and what you get if you turn a couple of graphics options down to medium or low; be sure to change graphics settings at the Main Menu, and quit and relaunch before testing.
The other option, if you can't stop the crashing with the current graphics card, would be to buy another one. There's not much point in spending a lot of money on a newer GPU, or even a never-used somewhat older high-end model, but you could certainly find relatively cheap options that should work well with your current system. Even as old as your computer is, it might still run Sims 3 reasonably well for a couple more years, provided the other components are in reasonably good condition. (And there's no reason to think they aren't.) Let me know if you're interested in going this route, either now or once you've exhausted other options.