It happened so long ago I can’t remember where I found the information.
I use a batch file to quickly delete the files and bypass the launcher (makes the game load faster).
So it’s perfectly safe to clear them out – You should always clear the cache when you delete CC and mods. The game will look for those files every time it loads, and will regenerate them if they can’t be found.
Just as it is wise to clear your internet browser cache from time to time, because it can prevent you from seeing updated content, it is also a good idea to clear out the Sims 3 cache occasionally, because if any of those files hold incorrect or corrupted data they could stop your game from loading. Cache files are temporary memory files created by the game to make loading times quicker, just like your internet browser stores certain information (snapshots) of web pages you frequently visit so they load quickly when you revisit.
