I began toying with mine back around 13 or 14. Over a period of time, they began having more and more of an influence on my own sexual response. By the time I was an adult and to this day, I pretty much can't cum unless they're being tweaked.
And I am drawn to a woman's nipples like a magnet. I'll be there until you tell me to knock it off. Lick, suck, bite, pull, yank, twist, whatever your pleasure.