I ride with just enough weight not to loose my stirrups. I mostly ride by balancing on my seat. I still feel stirrups are invaluable though. Without them my legs would get tired and I would get dumped at most spooks.
Going faster than a walk I use my stirrups more. Like I would probably find it hard to trot and canter without stirrups for any distance at all. But at a walk, sometimes my feet can slide out if I am pretty relaxed.
I remember when I started riding though I went through a phase where I used my stirrups as shock absorbers and put quite a bit of weight in them. I guess my riding style has changed over the years, and I think it's for the better. I think because I have better balance now is why I put less weight in my stirrups than I used to.
So it's probably a sign you have very good balance and are relaxed riding. Which is a really awesome thing.