I almost (mentally when in the field in the heat of the moment) rated the age of a deer by the size of their spread ... Telling myself that the bigger the rack the older the deer, the more value it was to take. Then I went onto some private club's land where 2.5 year old deer had HUGE racks, due to good genes and great deer management.
So, I started paying attention to the deer's teeth. And sure enough, those teeth age rating plaster molds work. Awesome.
A good tool to have, or to know someone who does ...
For me its all about the events that lead up to the opportunity to take a buck. It could be a tough, long drawn out hunt. A few years back this was the case for me. I thought I was on a great deer so I hunted him for 3 days in the rain, high winds. Turned out to be a 127" 9 point but I took him anyway because I felt pride for what I had done while hunting this buck.
I mainly care about filling the freezer but I don't generally shoot anything less than a 7-8pt unless it's late in the season and I'm behind the curve. Fortunately I haven't had to do that for several years now. (I probably shouldn't have said that, now watch)