Eyes open or closed? Open, almost indefinitely. I got bored around 30 seconds and stopped. Closed, I need a spotter or I fall over in 2-4 seconds. I'm told I rely too much on my visual cortex, whatever that means. I never would've known this if I hadn't broken my ankle. Scratch that, both ankles (several years apart). I'm sure having arthritis in both feet and weak ankles has a lot to do with it, too. I'm sure lots of people have poor proprioception, and apparently it can be improved with practice and training.