I ride my mountain bike 1500 miles a year with sneakers.?

I ride very hard, ave 19 on trails for an hour, but fundamentally I have many flaws. Most noticeable is that I don't use clipless or anything other than my sneaker on the pedal. I'm used to positioning my foot so that my toes and top portion of my foot are touching the pedal, completely different then how they clip in with my clipless. While I know this might not be the ideal way to ride, it's been working for me for over 10,000 miles and it feels very weird, especially on my leg muscles, so I don't know if I should/need to switch to clipless instead.....? I want to push myself to do my best, but not sure if I can do better by learning how to ride with cleats.....Thanks a lot for the greatly appreciated incite :)