They should be "healed" already--in that he shouldn't have any open sores or scabs on his ears. He should have smooth healthy skin on the edges of his ears where they were cropped.
But it sounds to me like you are really talking about how you can tell when his ears have stiffened up enough to stand on their own for the rest of his life--in other words, when can you stop posting?
What method are you using? We have a good method here that a lot of us use: https://www.dobermantalk.com/ear-cro...acker-rod.html
If you can post pictures of your posting job from the front and the side of your pup's head, we can probably give you some hints if you need to change the way you are taping his ears.
A dobe's ears almost always have to be posted at least until he is done teething--say until he is about 6 months old. Some dobes have to be posted a lot longer--it depends on the shape and length of the dogs crop in addition to how thick the cartilage of his ears is naturally. It sounds like your baby is only about 4 months old? So you have a ways to go still.
If his ears are leaning in that likely means that he has developed pockets where his ears join the top of his head.
Pockets will make the tips of his ears slant inwards like this /_\ Those will need to be corrected before you can even think of stopping posting. Check out the tutorial above to get an idea of how you need to tape his ears to get rid of the pockets. And then ask questions here
Because it isn't necessarily obvious how to post the first few times you try.
You really should learn to post his ears yourself. Most vets don't do a particularly good job posting ears. If his posts are only being changed once a week, that alone is a sign that he is not being posted correctly. And if the vet is telling you they don't need to be posted when your puppy is still too young, he is likely quite wrong (or your pup's crop is very short.) It's not that hard to learn how to post ears--and once you know how, you will be able to fix any problems that might show up, or fine tune the posting job immediately instead of waiting for your next appt.
The general procedure is to post his ears for 3-5 days (usually closer to three), then take them down, clean them up a little, let them dry out, and put them back up immediately. He should not be out of posts for more than about 30 minutes max. Resist the temptation to take them down at this point and leave them untaped while you wait to see if they will stand properly.
It is better to post for a few more weeks after you think his ears are completely done. You've put a lot of work and money into them so far--don't risk an eventual crop and flop by stopping too soon.
At some point, what you will do to see if his ears are "done" is to stop posting his ears one morning and keep an eagle eye on them. They should stand perfectly before you quit posting, and if there is ANY sign that they are starting to sag when he is alert and holding his ears upright, he will need to go back into posts right away for another few weeks. He is definitely not done if you are seeing his ears sag or tip inward--that will only get worse the longer he is out of posts, and at some point, you won't be able to correct them.
It looks like John beat me to it with his post above--I'm saying much the same thing he does--which means he's right