Samourai, my impression is that when testosterone is too low or too high, over a long period of time, there can be problems. However, low testosterone does not predict increased life expectancy. It is the reverse actually. I have not seen a study equating high test levels to increased mortality but we can extrapolate from individuals who use hugh quantities where they experience high estrogen, high blood pressure, eventually an enlarged heart and decrease in HDLs (your protective cholesterol).
When you look at it from the perspective of an aging but still active, athletic male, it makes more sense. Guys that are over 40 still trying to be as good as they can physically have the right to obtain benefit from hormone replacement if they have low hormones and it makes them feel and function better with minimal to no risks.