That sounds pretty good, as his stamina gets up you will be able to increase it slowley, but i would definatly stick to short and sweet, but regular excercise at first, like Rona says. You may find training sometimes seems to take backward hops the longer you get him - he may start off perfect then suddenly develop a naughty or rebelious streak, but Id say dont panic, this is normal as he grows in confidence with you Just stick to his training and dont get disheartened if he does rebel a bit later down the line. Consistency is the key