The only question that I can answer with confidence is why doctors are vague with a life expectancy.

The first reason is that everyone is different. Some people live a very long time with a disease, while someone else with the same disease might pass away very quickly from it. There are just too many variables involved when we're talking about people.

The second reason is because when doctors tell someone they have a certain amount of time to love, we'll say five years as an example, the person often worries, especially as it gets closer to that five year mark. The person can actually make themselves sick from the worrying. Many people die when the doctor predicted that they would due to stress more than due to their original disease.

So doctors are now encouraged to not give concrete time predictions when it comes to death.

As for what tablet he might be taking, you can check this site out and see if it sounds like what he might be taking. I don't know much about this.
http://www.prostateinfo.com/

This link has all kinds of links to prostate cancer articles. http://www.nlm.nih.gov/medlineplus/prostat ecancer.html