I've been playing guitar for over 13 years now, and I've always had a musical knack from childhood, though I was never traditionally trained to any extent. I had a few guitar lessons when I started picking the instrument up, and I've never had a vocal lesson, or piano lesson, at all. There are peaks and slumps of advancement along my musical path, some periods bearing more improvement than others, but it really all winds down to determination above all else: if one is dedicated, then it is possible to do nearly anything. I do not have a posted mix yet as of this date (to memory I only believe I have submitted two, and they were WAY back when in 2005 I believe), but I'm still working hard at it. One day, I'm sure it will pay off. Diligence, getting feedback, and working with others to improve and expand your musical realm are the best ways to get better.
It's very hard to condense musical progression to a single timeline, as the amount of time you spend improving is not necessarily consistent on a daily/monthly/yearly basis. I can say that the time I spend working with others for projects and collabs help me improve more than if I'm simply messing around on my own in that same amount of time. *shameless plug of how OCR brings people together and makes everyone all better, just like happy little elves*
To sum up this meandering and convoluted mess, I'd say it took me over a decade to get here, but the times are different for everyone. Good call on making this thready btw.