I think it is very normal and how long it lasts depends on the person. I was the person who said "I have bipolar, don't it?" so I got rid of the denial mostly before diagnosis but I had a kind of weird path to diagnosis which played a role in that. It was about 2 years from when I was clearly bipolar (much longer since it was possible to see it) until I spoke those words.

How long did you go undiagnosed after you could have been?