Going for 5 minutes must mean you had something on that stopped him using power or fury moves? I have used beast in attack in PVP and he keeps going forever unless he can use his power or fury move. Have had to take PVP losses myself when opposition has something like celestials/VHE and a power/fury stopper. So stopped using him like this. I do think that they should add a 'stop turn' button or probably more realistic set an upper limit on any repeat turns. Maybe 10?