I knew a guy who ran a reptile specialty store, but would take in sick snakes and try to help get them eating. Usually young ball pythons or corns that were being sold for like 5 bucks (you get what you pay for...) and likely had congenital issues. He said he'd tried force feeding when it got to the point that the snake was about to die, and he's personally never seen one survive after it got to that point.