My brother was 75 when he had to take a Lupron six month shot Before his SBRT radiation.

He continued to have hot flashes for about nine months after that six months shot expired. It took that long for his testosterone to recover enough to stop the hot flashes.

You could ask your doctor to give you a testosterone test every couple of months to see how it’s going. Some people recover quickly others take a long time, that would help you find out where you are at.