Over the six~ years I've owned my Wii, I've never noticed the vents clogging with dust. Not to the point of issues like overheating or malfunction, anyways. On occasion my Wii has had long periods of inactivity and still continued to work, even after obtaining a thick layer of dust (I blame Skyrim...). The dust won't be problematic so long as you wipe down the Wii every once in awhile. If you use your Wii very often, you probably won't have to worry about dust at all.