Yes!!!!!!!!!!!!!!!!! As long as appropriate screening for latent prostate cancer is performed, then older men can safely take it if they need it. Interestingly, there are new studies that suggest safety in localized cancer w/low gleason scores during active monitoring but this should definitely be discussed w/your uro-oncologist. But final answer is yes, men of any age w/low t can be treated safely w/benefit.
Window period. Hormone replacement can occur in older ages but it depends on your psa level, your prostate health as well as your overall health. There is a window of opportunity to intervene and prevent problems. The older one is, the less hormones you naturally have, the longer time there was without hormones so less of a chance to respond well compared to the younger men. Speak w/your doc though.
Another tricky Q. By livelihood I assume you mean salary or some productivity measure at work. Earlier this year, my cousin pointed out that wall street traders were looking for t supplementation to boost their performance (http://bit. Ly/xqjexf). A few years ago, a study purportedly demonstrated that t affects risk taking behavior in wall street traders. In sum, low t might decrease (work) performance.