Not always can instructing be paying dues. If one has only been instructing in a C-172 then jumps to a CRJ or something, they should pay a due again. Docs once done with residence can pick a field and again go into specialized training, ie. paying dues. About going from company to company flying, your experience got you the better job, but you still have to start at the bottom working your way up. I mean a CRJ capt. ( no disrespect), should not be allowed to go to the top or middle of FedEx. They should start on the bottom of the list because they choose to go to a new carrier.