Katie is right - the fact that PSA is very high at diagnosis does not indicate how successful or otherwise a treatment might be - someone could be diagnosed with a PSA of 10 but widespread mets and find that the HT only works for a very short time.
As a general point of reference, it is estimated that HT will control prostate cancer for between 2 - 5 years before it becomes hormone independent (castrate resistant) and other treatment has to be added. However, for some men, the cancer is hormone independent immediately and we have members here who have done well on HT for 10 / 15 years.