Do you do any outside gardening? I've had repeated problems with spider mites and decided that I am bringing them in from my vegetable garden. So far, knock wood, the littler buggers haven't shown up on my current indoor grow. The precautions that I now take: I only go into my grow area first thing in the morning before I've gone outside. I've even put a sign across the grow room door as a reminder lest I forget. The rest of the day, I stay out of that area of the house. I also put up a gate to keep the dogs out of that area in case they might carry some buggers inside on their fur.
I didn't realize until reading what eliz posted above that thrips could fly. So I don't know if this will help much for thrips but it might.....