On my first machine, it isn't hard to clean, and no danger of my messing it up. There is that danger on the Featherweight.
So, on the first machine, I don't really have a se schedule. So,I clean it about every 3 weeks, if I am doing a of sewing. On the featherweight, I can tell when it needs cleaning and oiled; it sort of "tells me" the way it is sewing.
Mariah