The number of years for me is irrelevant.
I have seen very “senior” (as in their 40/50s) designers that are really not mature at all.
And I have seen (and had in my team) an incredibly talented and mature designer that was in his early 20s.
So age for me doesn’t come into account, at all.
The way I see it is the following:
How much do I know about let’s say, usability testing? From knowing nothing to being able to write a book about it.
Well, I wouldn’t probably write a book and compete with Steve Krug just yet
But I did feel good enough to face a couple hundreds of people in a UX conference to talk about it, how we brought it in a big organisation, made it the norm and used it to involve high profile stakeholders. So not too bad, probably senior in that area.
I’d do that against the UX spectrum and see how I score.
(not starting a debate here about what a UX designer is … that a can of worms I won’t get any near of in this post)
But a simple version for me is:
- Junior needs direction and heavy mentoring
- Mid-weight doesn’t need as much direction, but still needs some level of mentoring and validation of work
- Senior sets the direction, inspires his team and mentors juniors and mid-weights.
Hope this helps!