> you can kinda tell where you should optimize ahead of time

Rules are "kinda" made to be broken. Be free.

I've been sticking to these rules (and will keep sticking to them) for as long as I can program (I've been doing it for the last 30 years).

IMHO, you can feel that a bottleneck is likely to occur, but you definitely can't tell where, when, or how it will actually happen.