Under most circumstances @ 225-250 would be around 4 hours total... give or take a half an hour.
Crust cracking, bones moving, and exposed bones are all good signs towards a finished rib.
Have cooked BB @ 300* (indirect) for three hours (unwrapped) - done.
Was there a deflector plate?
Cooking at Mason-Dixon BBQ Services
Lang 84 Deluxe Kitchen known as "The Glamazon" , Custom Klose Backyard Chef... of Snot, and a 22.5 WSM
Lang 60 Mobile - The Damsel II, Lang 48 Patio - The Damsel, Bubba Keg Grill - RIP, Double Barrel Smoker and a BSKD