100bb effective 'never' is a good shorthand description.

In live low stakes poker you can put some people's 4bets as KK+ only as a general rule so 150bb+ effective is where you start thinking about it. It's not as crazy as people make it out to be ITT. Problem is you have to be pretty sure the person won't make a 4bet with AK in order to fold.

These days even some 70 year old who looks like a retired librarian is capable of getting frisky so you need to have been watching their play.

EDIT

50+ year old women who open limp every hand generally only spaz with aces pre. That's about the most solid demographic read I can think of.

EDIT 2

I once watched a middle aged woman just butcher a couple of young guns because they kept trying to blow her off pots and she always always had it. The only hand she raised pre with AA, which she showed when everyone turbomucked.