Pilot & jogadaman,
Thanks for your thoughts on main beam length. I've since designated the 15" beamed 4 pooint - as a 2-1/2 year old based on other information from the are - including beam length and 1st circumfrence measurements. Interestingly, a couple bucks with only 12-14" beams were also put into the 2-1/2yr old category - based on 1st circumfrence measurements, and overall mass.
I'm sure our estimations are not perfect - but generally, we've decided that deer with 14" - 18" beams, are likely 2-1/2yr olds, bucks with beams over 18" are probably 3-1/2 yeaqrs old.
Thanks to everyone else who gave some input.