Do you think that I change the guessed age of trees every year? I have a few hundred trees that I keep records about. The age is an educated guess from the start. It can stay at 40 years for fifteen years and suddenly I decide to change it to 50 or 60 .What's the problem? It is still an educated guess. Age is not really as important as it seems. Amateurs look at it. Old age means the tree is weak and might die soon.