He sounds like he is doing fine for an old man
You would know if he needed help. There isn't much a vet can do about this, at his age as it is old age rather than specifically medical and there is so little treatment available other than for acute conditions. I think I would only take him to see a vet if he was suffering or injured.
Our first Syrian seemed quite surprised at first when his back legs gave way a couple of times (trying to climb into something) but he soon got used to it and they adapt.