Once or twice a year -- maybe.

A better thought is to put two drops of
Lanolin on your hands, rub your hands
together briskly then rub the strop
briskly... once in a while.

MWF is a fine shave soap and the lanolin
in the mix helps it build a fine lather but IMO
it is no more of a strop conditioner than
any other good tallow based shave soap.