I first became a "brony" when it first came out... I must have been six at the time. I grew up with the show up until Season 5 when I started to look at other interests. I was still there in Season 6, but by Season 7 I had moved on. I only came back once during that season when Starswirl came back, since it was obviously a big thing at the time. Then I forgot about it entirely.
It was only last September when I found out it was ending and went on a nostalgia trip that ended up with me getting massively back into the show now that I'm 15. That's when I would call myself a full brony, or pegasister technically.