When asked point blank regarding ADT with my Salvage Radiation, my RO said that "taking ADT would only give me a 3-5% chance of a better outcome than the radiation alone."

(post RP, lab said "Radical Prostatectomy - Pathology report Perineural invasion, and Lymphovascular invasion Stage pT2c, pNO.")
PSA had gone up to 0.091 from a low of 0.039
PET was Negative results for metastasis, but, it seemed there must be something growing somewhere...

He's a younger guy and seems to be up on the current stats and treatment. (it's a little annoying that he answer every question with a stat...LOL), but, I was really comfortable with him. A lot of folks I talked to thought the ADT was probably overkill.

My response was "give me all ya got doc!"

I'm off it (Orgovyx) after two years worth and for the last 6 mos my PSA has been < 0.006. So in my feeble brain, worth it. If/when it starts up again down the road somewhere, at least I'll feel like I did everything I could.

Now, do you "NEED" it at 70/80? I agree with most of the other answers, it depends on your general health and more importantly, what are you comfortable with.
Best of luck to you!