Vertical jump: have I reached my maximum?

I understand after training your vertical jump you can reach a max. Like where you can't improve anymore. I heard you can reach your max by jumping alot. I started jumping and playing sports alot when I was 10 mainly basketball I also did plyometrics once a week in gymnastics but that was only once a week for a year when I was 8 or 9. When I was 10 I measured my vertical at 18 inches or so it climbed gradually im not sure how much but at 15 it was at like 24 inches or so. I played sports very rarely for the next two years. now at 17 its at 28 inches or with a running start 34 inches because I have been jumping again and playing more basketball. I never really have worked out my legs or done plyometrics steadily at all. I just want to know have I reached my max limit or could I start doing plyometrics and jump training and raise my vert. open to people who know about this kind of stuff. thanks!