I've been a full-time developer since about 1993. I switched to 100% standing at work in 2014 sort of on a whim. Before that, I had a significant episode of back pain (enough to leave me unable to function normally) about once a year. Since then, never once.

I'm sure it's complicated and I know correlation is not causality. But my personal belief is that standing is a huge benefit for my back's health as a programmer.