Yeah, but the big key is to keep things instantiated only once (where reasonable). So, if I'm making an RTS, I keep only one list of selected units, and it pers

Yeah, but the big key is to keep things instantiated only once (where reasonable). So, if I'm making an RTS, I keep only one list of selected units, and it persists even if I have no units selected. No reallocation or losing the reference means nothing is getting garbage collected. There are bigger convos to be had about data architecture here, but now's neither time nor place for it.