I did my first deep clean earlier this week, after 42 roasts (22.5KG of green). I empty chaff box and clean chaff basket and cooling tray fan/box after every roast session. Impeller and housing had a dust film but nothing drastic, a few stray beans in the exhaust vent though, so something to keep an eye on (assume they strayed during charge loading??). Vacuumed a bit of chaff from vent under drop door, wiped dust from drop chamber. Used Cafetto Espresso Machine Cleaner powder in water solution and toothbrush for impeller and basket. Only drama was the taste next time I cleaned my teeth 
Had a bit of trouble with the Impeller cover plate screws going back in and a minor correction to get the cover re-aligned properly to stop knocking noise, but first time lessons will make it easier next time.