Took me 5 years... But I started riding when I was 3. Didn't start cantering till I was 5, and even then it was just a fun gait for me that didn't really matter-just kept becoming faster and faster when I rode because that's all I cared about! When I was 6 and 7 I actually started showing and realizing what I had to do, then when I was turning 8 we started over cross rails (ground poles had always been thrown in there, I had almost a flawless 2 point over them). So, it really depends on how you're doing. Plus, keep in mind, your instructor may have something totally different for you. I changed barns when I was 10, and didn't jump for a year after. I finally asked 'When do you think I'll be ready to jump again?' and my instructor informed me 'I dunno, we're concentrating on dressage for now.' and of course then I decided to be an eventer and I started jumping and doing dressage and cross training at age 12. Now I'm an all-arounder, my lessons change daily (yes, I do take 5 lessons a week.) and I'm ready for anything anytime it comes! Anyway, to get back on track-nobody can tell you how long it'll be before you start jumping, but always be prepared for the exciting day!
Eventing: the only sport where you wear your medical information strapped to your arm.