Fury has seemingly good stamina against C level opponents who don't make him work. Against top level opposition like Wlad Fury will gas out after 5-6 rounds because he will have to work much harder to avoid Wlads punches than punches from C level guys like Cunningham or Hammer. Fury will become a sitting duck by round 7-8 and will take one straight right hand from Wlad after another :deal
I don't see Furrys stamina being a problem as he will be taking a nap inside 5 rounds anyway. The only way he sees the last bell is if he trains just to survive and trains cross country style running so he can run for 12 rounds. If he comes to try and 'smash' Wlad...he will get smashed and quick. It will probably be something similar to the Wlad v Pulev fight...only with a better KO finish.