I wouldn't necessarily put a time on how long to shoot per day...just practice till he gets tired or till you see his groupings go from better to worse...then YOU know hes getting tired. if you continue on past the tired stage you can get BAD muscle memory...IMO...so its best to keep it light hearted and aim for the bullseye. Soon as he consistently gets vitals/paper plate to saucer sized groupings or better he should be ready...but just realize he might mess up the first shot due to the old adrenaline rush...also if you have an adjustable bow slowly crank up the tension every couple weeks...a little at a time and that will help build his bow pulling muscles and get him at a higher poundage which is also better for taking an animal...just my thoughts and be safe...good luck!