Alot depends on the crop being cleaned. Crop debris that has low moisture is naturally much easier. Debris that can heat and cake, not as much "fun".
There is pretty good access to the rotor area and auger bed. A leaf blower works well if material is dry.
The tuff spot in the hopper is where the rear cross auger feeds the vertical unload auger. Not much room there for anything but compressed air.
Same as the 915 if you clean the return and clean grain augers. Probably need to slip the chaffer and sieve out for that.
I'd guess you are looking at 3-4 hours, that does not include removing the chaffer and sieve.