3.5 to 4.5, I would not put him any older

1.5 nubbs and small body weight
2.5 nice antler development from previous year body is just starting to develop muslce tone and weight gain...
3.5 nicer antler development from preveious year body is starting to develop good muscle and good weight gains, should have a straight back with a nice pronounced brisket area and deveolping stomach area..
4.5 even nicer antler development from previous year, this is when a deers body is starting to mature , you will notice they will have a pronounced brisket area frontal, and start to put on some really good weight, and might even have a slight bow in the spinal area.....
5.5 and older Most have one hell of a rack not to mention very large bodies... the brisket area will be nice a fat and hang down just a bit, they will have a nice BIG fat belly and should by this age start to have a sway in the back bone area by this time in there age they are mature and ready to be shot.. some might even give them another year or two .. also by age 5.5 there teeth have started to degrade quite a bit and in the coming years will have a dirrect affect in there foraging habits....

Hope this helps some of your fellers...