I'd leave him in until at least tonight, that way he's in there for the majority of his Day 5, but still not a complete 24 hours. You definitely don't want him to relapse.
You may also have to treat a second time. With stubborn stuff I've had to treat twice occasionally, with a break of a day or two in between to let their little systems rest. :) He's a strong little guy, and hopefully this ordeal is over after this evening, thoughts and prayers continue!! :D