If you enjoy off-road, stick with it. Age, beyond fitness, has NOTHING to do with it.
I tried to follow Malcolm Smith up Pikes Peak during race or practice, forget which. I thought I had him until we hit dirt. Then he just walked me. I was 46 at the time, he was into his 70s. I was on a bigger bike, he was on a 250. School was in session.
Tail of the Dragon at Deal's Gap... Avoid it now, do a trackday.
Do not do business with Myrtle West Cycle... Not a reputable vendor by a long shot.