I was 16, and had my first go at a webcomic as part of a project in school.
Lo, it was terrible and I shall not speak its name, and it's best forgotten by the world, but I learned a lot while doing it, and felt a lot more confident going on to my next comic after I'd given up on that first attempt. I've pretty much been drawing comics constantly ever since, but most of them have been fanzines/self-published for cons. Grassblades is my first big ongoing webcomic since I was 16.
But yes, I've been drawing comics regularly for 12 years.
ETA: This just goes to show I shouldn't reply to stuff before I've had my morning tea. >.< You were asking specifically about my current comic! I've been planning Grassblades on and off for 6-7 years, but I've been drawing/posting since late 2014/early 2015.