HI Dave
You've hit a couple of things on the head there ;-)
Changing lenses: I only ever do so outside, quickly, and with the camera facing DOWNWARDS - EG bring the lens UP to it.
Thrips (Thunderflies) are a good reason for the reintroduction of DDT IMO

. Usually however I avoid areas where I know they are out and about, the worst I had was one of the little bleeders crawling inside the screen on the back of the camera :o :@
(As well as in my hair, eyes, and all over the bl**dy car - even still on it after a 40 mile blast down the M-Way)
They are a blight for sure!!
Properly set up, a range of between 100-400 mm should give useable results at airshows for example, and proper planning (EG get the static stuff when something boring is on) should mean you're not changing lenses like a madman.
Come to think of it, my £99 Sigma 55-200 is on my camera about 360 days of the year, with the f1.8 50mm getting some use when I can be bothered (not often) and the kit lens barely gets a look in!