Jonny I don't know how large his plague is, while mine spread to other plants and rooms in the house as well it's possible that this is also his case, unless his venting from outside straight to to the grow room. I invested a lot in making my rooms sealed after my painful defeat against white flies so you can get a picture of how severe it was and my current aversion and precaution towards pest. Cleaning after harvest is also a good practice and many consider it a must do because it keeps mold, pest and fungus at line, preserves your gear and most importantly allows you to find and fix the source of the problem when it presents. He hasn't killed all the white flies in the world as far as I know, and if he doesn't plan ahead or make the right approaches it's most likely to happen again anytime. You don't have to be that serious about your grow, after all attitude is a decision.