It probably depends quite a bit on environment. I have multiple pets (2 dogs and 5 cats). Not only does dust build up but hair (dander?) Does as well. Things

It probably depends quite a bit on environment. I have multiple pets (2 dogs and 5 cats). Not only does dust build up but hair (dander?) Does as well. Things that also affect it might be whether you open windows a lot or use an internal forced air system with a filter. And of course, how often you end up cleaning the fan and surrounds because of this. I bought a new case for my desktop system about 6 months ago. There has been visible dust buildup around the case inflow fan for a couple months now, and I should probably clean the outside and vacuum out the inside of the case.