30+ and I go from machine to machine using them all. My wife pretty much sticks with her Bernina or the 319K.
Right now I've got her using different machines I've worked on just to make sure they are in good order. Not sure but some of them may go on up for sale or be given as gifts. I want them as right as they can be. If anyone can find the week spot in a machine, my wife can.
Joe