Probably close to five years and she was maybe 6-10 months old when we got her. We don't do much training sessions anymore cause she pretty well trained as well as we want her now but in the beginning we did dedicated training sessions and each sessions started with a little laddering, "step up, step up, step up, that's a very good bird!" etc., then we'd work on just some interaction, giving almonds for treats when she let us touch her, verbally scolding and laddering when she was naughty, and we'd end our training session with laddering and much praise. We tried to do every training session in a certain spot in the house to help differentiate training sessions from just hanging out. While a mustache parrot is extremely smart for a smaller parrot, I would put her on the same level as a macaw, she's nowhere near as smart as a gray so you guys will probably have more activities you can do in the training sessions, whereas with ours it was more just behavioral stuff. Are you keeping his wings clipped or letting him fly some? Ours never flew when we first got her and we kept it that way until she was behaving very well and we knew she wouldn't use flight as a way to get away from us at the first opportunity, lol, then we let her feathers grow and did training sessions to work on flying and landing (nothing funnier than a majestic bird of paradise missing the landing on her cage and unceremoniously fluttering down the wall and *thump*, lol). When she got good enough that she would start to fly places around the house on her own we let her enjoy that for a couple weeks but knew we had to put a stop to that for her safety. So now we clip her then let it grow until she starts getting adventurous and clip her again so she has cycles where she can fly enough to get to a shoulder at the dinner table (and beg, lol) and fly back to her cage but little more.