In my experience, only the hatchlings fall most of the time. Just like human kids, once they start growing up and learning to coordinate themselves they really don't fall much.
Donuts used to fall all the time (small heights, don't worry!) when she was younger but now at 4 months old she's only fallen once in the past few weeks and that was because she was trying to be on my leg when I was wearing pajamas with a material that her scales slid right off of.
I feel like every "kid" could stand to fall a few times or else how will they ever learn how to explore? Which is understandably not an issue for BPs that are kept almost exclusively in their tubs but I like my Donuts to explore.