When I've got a game I want to continue for a long time EVERY time I save I add a number to the end of it. I usually end up with hundreds of saves but I keep them all because I record them and make videos for YouTube and I often need to go back to the save I was on when I recorded the video to see what was actually going on or to rerecord something that didn't go so well in the original recording for whatever reason. Mostly because I actually failed to record it at all.
Since I know I'm most likely going to have hundreds of saves and I want to be able to sort them in order I use the same file name prefix for every save. Such As IP_Household then I add the numeric suffix. The first save might be called IP_Household001.sims3 and the 10th save would be IP_Household010.Sims3 and so on when I get to the 100th save it would be IP_Household100.sims3.
You don't have to keep all of your saves if you don't want to go back to every one of them so you can pick 5 or 10 numbers and cycle through them - or just delete the earlier ones once you're sure you don't want the keep them.
I always only have a few of the saves in my Saves folder. The Rest get moved out to a different backup folder that might be on my PC or on and external hard drive. Wherever it is saved I can always put it back into my active Saves folder whenever I need it.
I've recently come across some old saves I had burned to a DVD. They are from June and July 2009. It was a lot of fun to open them up again and see my old sims in action.