Hello. I'm trying to use the S3PE program to clean up my game files. I noticed there's a lot of useless image files in there that I've been trying to delete. (Everytime I went on vacation it copied all these images, so there's 13 versions of each one. Also that nonsense CAS does.) Basically I opened each file, searched for IMG tag, deleted the junk ones, and hit save. So looking at the original and the modified version, it goes thusly:
Lucky Palms_0x08866eb8.nhd - 92.7MB to 53.0MB
Lucky Palms_0x08866eb8.nhd.orig - 270MB to 48.7MB
TravelDB.package - 359MB to 17.2MB
Overall: Folder size from 818mb to 214mb

Yesterday the game was working very well, I managed to load my neighbourhood in just 15 minutes. However, now it's really slow again and I can't figure out why. It's over 24 minutes, and the loading screen keeps getting hung-up, stuck on the same tooltips. I've deleted the cache files too, so I guess it needs to repopulate those? Will it be faster next time I load the game?

My 2 questions:
-Why so slow? Was it wrong to modify above files with S3PE?
-I lost the thumbnail for my family, as well as the house thumbnail. Will this reload eventually? Also can you force a Comm lot to reload the tiny building visible on Map Mode?

The game always lags A LOT after mass-deleting resources in S3PE, because it's struggling to regain the resources it still needs. I've found that the following resources are generally safe to delete:

IMG: I'm not sure what the other files are for (they look like texture maps or something), but photographs, greeting card/prom/photobooth pictures and still life paintings also have the IMG tag. They're safe to delete, but you will permanently lose them unless they're saved to the Library.

SNAP: These are the resources that are used for Sim and household thumbnails. It bloats up something fierce whenever you use the CAS or Stylist tools, so I'd recommend cleaning them out every time you finish a session where you used these features. The game will regenerate only the ones it needs when you start it up again, but it'll lag for a while.

ICON: These are the thumbnails for lots. The game makes a new one every time you edit a lot, delete it, or make a new lot, so it can also bloat up your game pretty fast. I recommend deleting the ones you don't immediately recognize as being locations in your town (or that are empty lots), especially if you've closed a session that had some heavy construction projects with Edit Town. Like SNAP resources, the game will regenerate the ones it needs on startup, but it'll cause lag.

Partial:

I am an SP3E user, (not an expert) and would not want to attempt to clean up files in game using that application. I'm not even sure that is a recommended tool for cleaning the game folders. I only use it for editing. I hope you have a back up copy of your Sims Game Folder.

Why so Slow? I'm not a fan of deleting those cache folders on a regular basis as the game has to recreate everything upon load up and that can take a long time. Of course, if installing mods the script cache should always be clear. If you have removed those .nhd files your Travel saves are gone.

In the meantime while waiting for others to respond on your S3PE question there are a lot of tips for cleaning up the game in the Tips For Better Game Performance document: with links to applications suggested for cleaning - Mods that help - File and game management, System Tips, etc.

There's a useful tutorial on using S3PE to clean your save here . Those of us who've been "upgraded" to 1.69 might find this useful as Kuree's Save Cleaner doesn't often work as it should anymore.