Munchy is gorgeous!!
Hmmmm - old - some birds start to get arthritis and it begins to get harder to fly/move. I have a rescued 56+ year old Panama Amazon, Chico, who has bad arthritis in his legs so I have had to adapt his cage because of his disabilities - he falls a lot because the locking mechanism in his feet doesn't work any more. He is also pretty much blind which brings me to another aging point - older birds can get cataracts in their eyes - often you can see them easier in photos of the bird. If Munchy has a good diet and is able to regularly exercise he'll be protected somewhat. I see he is flighted which is great for him exercise wise. Can he get out in the sun a little? Or does he eat eggs? I'm thinking of protecting his bones with Vit D/calcium. As for being ill, that's so great he's never been sick. Sick birds are often less likely to move and sit puffed up, perhaps on two legs rather than the relaxed one leg. There might be discharge from the nostrils. Checking droppings should be a daily routine - droppings/poops tell you so much about their health. It's also a good idea to weigh them so that you know something is up if the weight changes. I know Munchy has never been ill, but it would be good to earmark or register him with your nearest Avian vet in case of an emergency in the future. Avian if possible, if not, exotic or ones with an interest in birds. I got caught out with a sick budgie some 20 years ago - I rushed him to an normal emergency vet who hadn't a clue what was wrong, but was able to recommend an avian vet who immediately diagnosed chlamydia and therefore we were able to treat him just in time.
Hopefully Clueless and others will have more to offer.