Does it matter how many Saves I have?

I don't know the answer, but I have the same question. I too do rotationally, and in addition I make several temporary saves for specific settings/scenes regarding video making. Back in TS3 I experienced better game performance after deleting 75% of my saves. Maybe that would help in TS4 too?

I don't have the time to experiment until after Easter, but you could simply back up your game, then delete most of your saves to see if game will speed up. Afterwards it would be easy to replace the backup. And, do remember to post what you find :)

Adding: I think also number of sims will matter. Because I got very close to 200, I chose unlimited, and I now have more than 200 played sims, plus a feeling that the game adds more and more npc sims. There is probably little culling when set to unlimited, so my goal is to go back to 200 as soon as the many elders are dead ;)

Not sure on the answer. I play rotationally and use 'save as', but I tend to delete any older than about the last 6 saves. If you didn't want to do that and were worried about a full folder, you could always move them to another location on your computer.

I keep some old saves elsewhere, and also the saves I set up to be my 'starter' worlds. Then I just copy them back into my game saves folder if I ever need to use them again.