Hey Marc, thanks for asking me this! Writing my 'why' page was on my to-dos and this helped me to make the content more useful. I essentially wrote it in response to your question today.

This may not be the scientific answer you’re looking for but most people who ask this question are under the impression that stance fixes your posture by itself. 
It doesn’t.

Stance should be used in bursts to get you used to sitting up straight and it will gradually train you to keep your shoulders back naturally without the corrector.

The improvement I’ve seen in my posture since using Stance is due to being more aware of when I’m slouching and correcting it as needed.

Stance plays a role similar to training wheels while you’re learning to ride your bike.

It shows you how it should feel when you’re sitting correctly, but ultimately it is still up to you to consciously make an effort when not wearing it.

Also, for the first time in my life, I was randomly complimented on my posture (by a friend who didn’t know anything about stance or my experiments) which felt really nice 😁

www.getstance.com/pages/about