Well, I only learnt that being a furry was a thing shortly before I joined here a few years back, but from my earliest memories I can remember certain games and cartoons affected me in a very visceral way. Things like Kimba the White Lion and Disney's Robin Hood seemed different to the background of other cartoons (even those with anthro animals like Goofy say) and when I did what I would now call RPs with my friends I would often be a "furball" character while they would be superheroes and human characters.
So I would have to say my whole life.