I agree with you John I am a bit concerned about pumping dust all over the primary on regular basis! I know a little bit of dust (or even a lot sometimes) isnt a big deal - as it only covers a small portion of the total surface area of course - but i do subscribe to the theory of not washing your mirror very often - a Pain in the neck process - plus it quickens the demise/oxidisation of the mirror coating? - i have heard the modern mirror coatings are much tougher and better but.
A gentle fan at the front end of the tube - pulling the air out - has been suggested to me - but i dont know?
Kearn