Vicki, This will be long. I adopted 2 YNA males ~ Macho 18yrs and Midori 17yrs in early September. They were raised together now reside separately as Macho was quite the bully. They join my 
Sunni. I had huge reservations about this. I have been lucky enough in the past to share my home with two Tiels, one U2, one B&G, one precious handicapped WFA, one CAG all at the same time with my YNA. I cared for all the above wonderful companions for about 4 or 5 years and then became horribly allergic. I had to place all but couldn't part with Sunni. I share this so you will know that I've had a little experience with some of the other breeds. I really think that the zons are a little more resilient than some of the others. At this point I know that Macho is a masher and I will only attempt to allow him to step up on a perch with a "covered handle" because if he can bite me he will. However every day when I clean his house, change the bowls, or toys he just ignores me for that period. Now I'm not going to assume that he would not go after me and I have my eyes averted to him while my hand is in his house. I don't actually know if I have shared their complete story here. While not abused physically per se, they lived in a vacant house (it had water and electricity) in a flight about 5 feet wide 5 feet deep and 8 feet high, with the light on and the T.V. pulled up next to the flight and on 24/7. They were given fresh water and seed every other day. For Five Long Years. How could I not attempt to take these guys allergies or not?
5 years alone and the 10 before that they were not handled. If I can never hold or scritch Macho I can live with that. I hold out hope that I will be able to handle Midori, he will step onto my arm and sit quietly for a few minutes but still doesn't want me to touch him.
I learned quickly to announce myself before walking into the bird room. They were not used to seeing someone and would get so startled it scared me they flapped about so. It was actually a friend that I adopted this guys from and she asked me not long ago if their screaming at night bothered my husband. I had to tell her that they really didn't do any screaming.
I share all this to get to here. I know these are wild animals and don't have our thought process. However I can't help but think that they appreciate the conditions that they now live in.
When I started working with them I did not want to begin with a routine that I would not continue. Some days I might not spend but 30 minutes with them, others - hours. I think with your guy if the routine that you started is the one that he will have if he continues to live with you, you are seeing what you have. If you next month decide not to let him out at your desk and he doesn't have the level of your attention he has now, he very well could become a screamazon.
He sounds precious and I hope he's found his forever home. 
Thank you for taking the time to write all of that. It all makes sense. There are some things that I didn't mention and probably should. I am a training and behavior geek, I know most of you guys already know that
IF an issue popped up I would work on it and I would be sad if he had an issue but I would enjoy problem solving it and figuring out a way to improve things. I think that the only thing that would be an issue would be if he screamed because then it would affect my husband too and that is the only thing he asks for, that I not have very loud birds.
Oh your poor guys. It was good of you to take them and both of them! It must be so much better and more comfortable for them.
You make a really great point though about being careful to make sure that I am doing things how they will be done in the long run. I am thinking that maybe I should have more days when I leave him in the cage more. I usually have him out on his stand when I am home and I am in and out of here all the time. When I am gone, he is in his cage. But, maybe I should have some days where I have him in the cage more to prepare him that there could be days like that....what do you think? I don't know too much about Merlins prior homes. From what I understand he was with his previous owner for 18 years and kept in a cage because she was fearful of him. I am pretty sure she didn't give him anything to do. Then, he was at the rescuers home for 2 or 3 months. She told me he improved with her as far as his stepping up and being able to get around better on the stiff foot. She told me he is only loud when he is hungry and you are getting his food ready. I was told he didn't like toys, but he is starting to chew on the wood toys I have been offering him and going through his forage box. To be honest, I don't hold him that much. He will step up but I can tell that it is not easy for him to balance on a hand. I typically take him out and put him on his stand and mostly just move him around because like I said, he just doesn't seem that comfortable just sitting on my hand.
When you started working with your guys, did you have them out more on some days and less on others? Is that how you prepared them to be flexible in their out of cage time? I think that this is an important thing for me to do for Merlin.
