Hello Redmare,
Sorry for the late response. But you can also export them, and then go to your Sims3 folder and look to the Export folder, there you find your family or house. Then you could save it to an external drive so you have them always save on a place were you can find them again.
When your PC or laptop does give up, simply move the Sims or house the your Downloads folder and install the Sims back to your game. Then you can play with them again. Hope it helps you.