The actual lot filesize really shouldn't matter unless you are sharing the lot. I'm assuming you've got a lot of custom content for the file size to be that big though.

Now if your game is slowing down on this lot, you probably want to look at some of the stuff on the lot...Some of the Maxis stuff can even get a little high in the poly counts sometimes...

I think what we need is a Body Shop that actually lets you edit sims and their wardobes instead of just make custom junk.

Long story second. I HATE elder Sims. ...I meditate them to death or just outright kill them.

I've had this happen once or twice...  Thing is, next play session the furniture will have returned.  It seems that the room somehow gets stuck on invisible mode, but the furniture is still there.  Reloading usually helps.

Could it be because they only tend to get memories of the first child in a family going to college?  That's always irritated me, the fact that only the first one is recognised.  Maybe it has something to do with that?

I don't really have evidence to support or refute this, at least not in my game. This is actually the first time that I have ever sent more than one child to Uni from the same family. When I searched through the memories of the rest of the family that was still at home, they had the 'artificially added' memory of "Went to College" that really should have been "$Sim Went to College" for this sim that I added to the family via SimPE. They had correct memories for the first sim that I moved to Uni in-game through regular gameplay.

I also read somewhere recently that if the new YA doesn't move into the same dorm, the want won't be satisfied until the other Sim either talks to them on the phone or comes into physical (pixel?) contact with them.  Did this actually happen in your game?

That might be a possibility since, when I moved the 1st brother into a separate dorm, I probably did have phone contact between the sister in the other dorm. However... I am fairly certain that I also had the 1st brother call home and speak to his other sibs and his parents... none of which had memories of him going to college. BUT... I did not actually go and play the home lot. I Did play the sister's lot. Maybe... if I had gone to the family lot in Pleasantview and called him from their side, it might have made a difference? But if it requires playing the 'other side' to make sure the memory gets distributed... I don't think I had the sister contact the 1st brother when I played her dorm. I just entered her dorm, right after I had moved him in, and the want was immediately satisfied. This led me to believe that the want for the 2nd brother should have been satisfied the next time I just entered her lot.

Maybe something similar with your problem, since I have the same problem as you, only having some of the teens being recognized as going to college. I've even had the parents not recognize that their child had left the nest for college and their want was still locked.