Mick if they are getting along ok now i would get him vasectomised now , he may be ok to leave in all year with the jills, my hob was fine and lived all year with any entire jills , he brought them out of season as & when needed, only draw back now is he may still be fertile when the jills come into season, maybe better if you seperate him after his op for a good 6 weeks , but by that time the jills will be in season no doubt anyway & need bringing out of season some other way