No. Jack being secluded and depressed for 50 years without positive contact from the many allies he made in the first 4 seasons was already questionable. Then the concept became retarded when it's revealed that Jack never bothered to look down the hole he dropped the key to saving the universe. Seriously, Jack had lost his sword plenty of times under really bad circumstances but somehow just dropping it down the center of an empty mountain was enough for him to give up? Plus, what was the point of aging him up if they were just going make him look the same halfway through the season?
They could've just had him look down there, see it had disappeared, and had him be a bit mopey for a couple of years. The 50-year time skip added nothing but cameos of elderly side characters.