Not to be contrary, but, there is no real defense on walking out on your job for two months. I can't think of anyone, that's not the star of a show, ever doing that. Remember Howard did say if the show sucked without Jackie, so be it.
They fired Opie from his own show for the very same reason.

Jackie used to take over the jock lounge for hours after every show to make endless phone calls related to his 47 companies that made no money.