Very interesting thread.
I also do want to add on, no clue if anyone else has mentioned this yet or not. But the longer you play your game, the more memories you accumulate (which does include nonactive sims), the more laggy it will get.
I never experience any lag issues because I use Twallan's MC to make sure no memories are produced. One time I played a game for a while (I think for a week or so) I get such bad lag EVERYTIME I load up my game and it was ridiculous. I started a brand new vanilla and been playing my game, making sure no memories have been produced.
Also, because of my video card and my pc rig, I will occasionally get lags using CAST for a long period of time unfortunately. But I'll deal with it >.<
