LAST EDITED ON Dec-05-08 AT 05:41PM (MST)[p]There really is no rule of thumb. Basically, when they're yearlings their horns are tiny. When they're two their horns will range anywhere from 60-85 inches. Their peak horn growth years are between 3 and 6 depending on the area they live in, the weather and forage conditions, etc.
If you see an 80-incher in an area that usually doesn't produce bucks over 80-inches then you can probably count on that buck being about the same size the next season or perhaps even smaller.
If, on the other hand, you see an 80-incher in Arizona's Unit 10 (or similar unit) then that buck may be anywhere from 75 to 90-inches during the next season depending on all of the above mentioned factors.