So, Dr. Whatshisface conveniently has a bottle of Fountain of Youth water mailed to him and - instead of using it on himself - he uses it on his rotting douchebag friends. They're rather pleased with the results until it wears off. Then the old codgers go trekking to Florida to find more. There's a moral lesson in there somewhere, probably, but Hawthorne tends to be so dull that I didn't really notice.
I assume they eventually gave up on their quest to find the fountain in Florida and spent their few remaining years at Epcot, drinking around the world.