Timely post! I have been pondering this 2-year mark as I just passed it a couple of weeks ago in PACU (went in as a per diem new grad), and I have a few things to add.
First, I may be the exception to your rule, because I am anything but overconfident. In fact, I get frustrated with myself (and the docs get frustrated with me, too) because I feel like I'm still asking too many questions. The other day a nurse "excused" me from helping with another patient because I needed to get mine transferred, and it reminded me what an albatross I still am. The nurse came back to talk to me later and said when she was starting, it took almost 5 years (like you said) for her to not feel that way. I don't resent that people feel this way about me, because I know it is true; I'm still a drain on the system, and I don't want to be! Seems like I "should be better" than this by now. I'm too old to go off half-cocked to look more competent, but the alternative is to be underconfident and slow. Safer, but still problematic.
Second, 2 years is a weird place. I'm not a new grad anymore; I now have too much experience to take a new grad or residency type position in any department. However, do I have enough experience to do anything else? Doesn't feel like it.
Third, the good part: there are little moments when I know I'm getting there, like making a good call on not giving a PRN med, catching an incorrect med order before the patient went to the floor, or having a good reason why my patient is still in PACU after 2 hours and not having the charge nurse tell me to throw them out! Those moments come closer together these days, and the number of patients I can just take, recover, and transfer without fanfare is growing.
I will keep your words in mind. One of my wisest colleagues once said that the day she didn't learn anything new would be the day she retired. She did retire this summer; I had suspected she in fact knew everything...