Having just returned from a trip to Kenya, the most dusty country I've visited so far, I'm happy to say that my sensor doen't even show a hint of muck anywhere. I'll check a bit more throughly after cleaning the exterior of the body properly when I'm less tired, but after swapping between three lenses numerous times I was expecting to have some sort of build up. The lenses may be more of an issue, and obviously more troublesome to clean (except the prime) but I think being a little OCD with bags, caps and lens changes has paid off. Just yesterday I spent 6 hours climbing and trekking around the rim of a dormant volcano in the great rift valley, surrounded continuously by a cloud of ultra-fine volcanic ash.

I have just discovered an irritating spot of dust on my sensor. Arrgh!
Now to decide what to do about it. Im a bit to OCD to leave it alone.

Blow it off with clean purified air from a lab. Otherwise use a tyre inflator from your nearest garage.

well i've cleaned the sensor and its still functioning