I'm one of those who didnt bother with some dust because I never shoot beyond f8, SC five-digit.
Then one fine day 'gay-kiang', decided to use blower to blow sensor cause thought shoud be safe, who knows one big piece of dont know what dust dropped onto the sensor, yes I was careful or so I apparently thotso, ..anyway even f5 also became very obvious lol
Send in only say 'clean sensor cause dirty', but when I got back sensor is cleaned, plus its written shutter mechanism changed. Friday sent in, Wed collect.