HT will only work for a few years, sometimes as few as two, usually less than five, but occasionally over twenty. So Radiotherapy, HIFU, brachytherapy may all cure you but HT will not.
Prostate cancer is a slow disease, you could opt for active surveillance, if it isn't getting worse you may live a long life anyway. If it does need treatment I think you should still aim for a curative one. If no curative treatment is possible do not go on the HT until you are getting unpleasant symptoms. By which time the cancer will be widespread, but at least you will have had fun up until then, and may get a few more years.