Sometimes sims bring the most RANDOM people over when they "bring a friend." Once, my sim called over his professor and the professor brought my sim's grandmother with him...I'm pretty sure she's never met him before in her life. (She was a CAS sim..so no university)

I forgot you used transitions! That's definitely easier than using actual ages. (I'd imagine it can get pretty confusing when you actually use years.)

I don't get much lag at BV lots..though, the last time I went to a BV lot was around the time FreeTime came out. So who knows how bad it could be?