I wore my fakes full-time for eight months (an average of 21-22 hours a day), from the end of June last year until February. I only stopped wearing them because I started actual orthodontic treatment at the end of February. Initially, a friend challenged me to wear them all the time for one week. She expected me to give up, but I didn't, and we continued the experiment. Many people enjoy the loss of control that comes with wearing fixed braces. I enjoyed the discipline that came with wearing removable appliances. It made it more realistic to have to follow some rules.
My braces were prominent, but disappointingly, only a few people brought them up in conversation. I suppose adults with braces aren't big news anymore. They were based on Hawley retainers with upper and lower (passive) expanders, a passive Herbst appliance, and a tongue crib. I was surprised by how quickly I adapted. I never quite got over the tongue crib lisp, but it wasn't a big issue, and I had no problems at work. Interestingly, neither my dentist nor hygenist noticed anything, even though I only removed the braces immediately before my appointments.
Overall, it was a very positive experience, and once my real treatment ends, I will repeat it in some form.