Realistically it's plenty fine. Not going to hurt anything, that's dust sitting on housings, not heatsinks or thermally sensitive components and circuitry. It's intrinsically no different to a car getting a little dirty, it won't stop the motor running or do anything to stop the tires turning. Only time dirt hurts a car is if it's packed with mud etc. Same thing for a pc. Dust is just ugly, for the most part.