That's excellent news!
I'm also in the 'exceeding the prognosis' club, I was told 3 to 5 years when I was diagnosed back in January 2019, six years ago. I had just over 2 years on enzalutamide, while taking it I thought I was fine but when I stopped (it wasn't being effective in keeping my PSA suppressed) I did have more energy and felt less tired.
Keep on keeping on: as Deckard (Harrison Ford) says in the voiceover in the film Blade Runner, 'We didn't know how long we had together. Who does?'