<don't think it is a myth. When I was repairing mine I saw that the action
of resetting made that part of the mechanism move in the opposite direction
from which it 'normally' moves in advancing the odo, etc.
There's a certain amount of slip in there but I could see how continually
resetting it at speed could eventually loosen the gear.>

The guy I was parked next to at Natural Bus a couple of weeks ago told me he had just reset his the day before while moving and it hadn't worked since. Good enough for me!      Jeff