I do not leave my machine on when I am not sewing etc., as a matter of fact I unplug it every time because of electrical storms. I do not want lightening striking my house and ruining my computerized sewing machines. And as someone else said, I have a janome 9000 for ten yrs and no amount of moisture or lint or anything else was in it when I took it apart. It too is a workhorse and I use it occasionally as I have now updated to a 10001. Marge in Pa. where we do get rain storms with lightening frequently in the summer