Personally, I would want to know my bird for more than 3 weeks before I would let him on my shoulder and near my ear. There is also a big difference in my experience between trusting him on the shoulder while your stationary like sitting on the couch as opposed to walking around, going by mirrors, picking up a cell phone or a mop or vacuum.
When I first got Nike I noticed that she liked being on the back of the couch. I would sit on the couch and she would run back and forth. Eventually she started climbing onto my head and after that down to my shoulder...it was all her idea as she became more comfortable with me. I learned very quickly that my ear was in peril if I brought a cell phone close to my head. Strangers would also cause her to get excited and possibly grab my ear.
Once comfortable with being on my shoulder the next step...which was more difficult, was getting off my shoulder. Putting my hand there and saying step up seldom worked and I would have to lean into the back of the couch or a perch and allow her to step off.
Eventually as we continued to bond I was able to get her to step up and remove her.
Walking around was easy but and doing things like house cleaning required a conscious effort on my part not to startle her.
Nike now never bites me hard enough on my hand to really hurt but it doesn't take much pressure to have a sharp beak cause a lot of pain and blood on an ear lobe.
Just take it slow and be careful. Now I cant walk out of the room without her flying after me and settling on my shoulder.