Depends when they are measuring it from and to, Philip.
From diagnosis (or from the point at which metastatic recurrence is identified) to death is probably more like 8-10 years - some members here are beyond 15 years. This assumes that the person is put on HT for the first time, or HT is restarted
For men who are already on long-term HT when their cancer progresses and becomes metastatic, 5-6 years is a good outcome - many will not last that long. It used to be that metastatic progression to death was 2 years at most but so many exciting and novel treatments have been developed so more men are living longer.
For a man who has metastatic PCa and then becomes hormone independent / castrate resistant, 2 years is probably about right - research / trial data for treatments such as abiraterone, enzalutimide, apalutimide suggest that, if prescribed after the man becomes hormone independent, these treatments can extend life by between 3 - 18 months