Great question Daisy, I would love to know too, since I am in the same boat right now. I\

I turn mine just a little when it seems that they are not cutting, I probably do this once a month or so. But mark your wheel with a sharpie before loosening so you only turn them a little bit.

I've been marking mine with a sharpie, but the marks have come off. MAybe I need to make bigger marks. When you say "seems they aren't cutting", Flag, do you mean that they seem to slip from the surface? Mine are kinda doing that too even though I've turned the wheels....Also, mine take out a chip instead of starting a clean cut. The wheels seem to be not quite meeting too. I know I shouldn't need new wheels for all I've used them, but.....?