As soon as you're getting set-mining odds
in a 3-bet pot, I'd say you're pretty deep. So 150bb's or more I'd say.
After playing nothing but 200bb's deep for a month, I much prefer either being 100bb's deep or 300+. 200bb's deep is just an awkward stack size where you don't have to have the nuts to stack off, but people can still set-mine & suited connector you in 3-bet pots. Such a weird & awkward stack size. And so much bluffing becomes possible when stacks are 200+bb's deep, since stacking off with 1 pair hands is a fast ticket to broke.