Coffee-tree age is one of many farm-level details that may interest a buyer. CoffeeBox's guide contrasts younger plants, mature trees and older plantings while considering their possible influence on production. Age interacts with variety, pruning, nutrition, disease and growing conditions; it does not independently determine sweetness or provide a universal ranking of cup quality.
A very old planting may have cultural or agricultural significance, while younger trees can also produce excellent coffee under suitable management. Ask whether an age claim concerns the original planting, the current stems or an average across a field. That makes a farm story more informative than an unsupported old-tree premium.
You cannot establish a tree's age by finding a gap in mid-palate sweetness or a short finish. Taste those qualities as qualities of the brewed coffee and use documented farm information for the agricultural background. When brewing, adjust to the actual roast and result rather than following a special temperature rule merely because the label says young or old.

The conversation
A good question can make a better brew.