Never have covered a machine in all my years of sewing, except for my first one, which was in a cabinet. Why do you cover them when you are working on them all the time? The machines have their own room, and they need to talk to each other when I'm not there! They couldn't do that if they were covered!
I cover mine because I live in the country and everything gets so dusty and I'm only using mine in the evenings and week-ends. Just helps keep it clean.
Shirley aka buckeyequilter I work to support a sewing habit that I don't have time for, because I work!