The word "expert" is an interesting one. It denotes someone with a high level of skill and experience in their field. It also, as you've said, is a hint that someone is "done" - they've climbed their mountain and are standing at the summit.

Personally I believe it's not a word anyone should give themselves. You're only truly an expert if lots of other people in your field believe you are.

I prefer to call myself a specialist, not an expert. Being a specialist does not preclude continuously learning and growing. It's more like farming a plot of land than climbing a mountain. The former takes work and effort, and you can get more and more out of your field.