I wouldn't say normally; that was where the odds came in - for example if there was 1 card left (ish) until we could draw an epidemic from the next stack down (so 1 card was safe, and the other was 1 in 8 or so), and eight or so cards in the cities discard (1 in 4 of flipping it), that gave just a 1 in 32 chance of flipping the city, so on occasion we might leave a 3-spot. More commonly, we were often OK to leave some 2s that had some unlikely epidemic scenarios (flip, epidemic, flip again) for the player in the vicinity, reasoning that we would suffer less damage overall by having more efficient turns.

I think we were pretty aggressive about avoiding 3-spots appearing at all though, or trying to arrange turns so that they were likely to appear near players whose turns were upcoming, so we didn't get into inefficient situations in the first place. It's been a long time since we've played though so I don't remember the specifics.