Fwiw--I always clear out my caches after every gameplay session, & then delete the trash folder. I have a number of different save-file sets, most going back to 2014 or 2015. Current one I've been playing is one of the 2015 ones. It has a lot of bugs, but it's still playable.
eta: I rotate between 4 different 'save as' savefiles for each one of my interconnected-worlds (need better terms!). So for the Kozlov-Pettifogger-Rudenko-etc. set of households, I have 4 different saves & I save about every 20-30 minutes, one after the other & back again. I used to have a different save for every household, but that was because I was expecting TS3 file-structure. I cut down to 4 because there are 4-to-a-line in the save-menu-box-thingy.
Also, before every patch, I copy my entire 'save' folder from TS4 over to the EA folder (one level up from the TS4 folder). That way, if my files get corrupted, I don't have to go back to the very beginning. I only started doing this a year or so ago, though. I keep those pre-patch save folders, too, just in case. At the very least, they might be useful to QA if they want before-&-after savefiles. (QA does sometimes ask for savefiles when they can't reproduce a bug themselves.)
