Early on, I only had 1 game save I played, unfortunately, I got a couple of EA bugs and also developed game bloat, that's where the save file gets junk in it so that the size of the file increases dramatically. So I had to recreate that game from scratch by transferring my household and lots from the old save to a brand new one.
After that I researched backing up my game and other safeguards to prevent corruption. There were several things I found out.
One, was the previously mentioned strategy of using the "save as" function periodically, instead of just using " save" over and over. With the " save as" you can rename the file i.e. Save 01, then Save 02, Save 03, etc. I personally name games using the surname of my main played household.
Another thing was a mod that would "Auto Save" my game on a shedule. This came in handy because I used to get a lot of crashes.
The game has changed the way saves work since then, but one issue I had in the past was having one save overwrite another, however, making sure that every save file has at least 1 household marked as "played" every time you save is a fix for this, I have found.
A few other things I do, I have an external HD where I have back ups of my files, from the "documents" folder on PC Sims 4 folder, I back up: saves, tray, mods, screenshots. With these I can effectively replace my game play from scratch. Also, custom music, if you have any you use. I keep my " tray" folder empty, this cuts down on loading screen times and lag. As its backed up, I can always put the files back if I need something. I periodically delete the thumbnails in the "cache" and "cachestr" folders, and most importantly, delete the localthumbscache.package anytime I add or remove CC or mods or just whenever the size seems to have increased significantly, that thing can cause bugs, none of these will harm your game if removed.
One more thing, making sure the household and personal inventories are not full of items this helps with the game lag and potential corruption.
Since I have been doing these things, my game performance is better and I have not had any catastrophic issues, knock wood.