My poll should have been 'one or a few weeks ago,' I accidentally chose 'more than 10 years.' I would say that I see an adult with a retainer every couple of months or so. A couple of co-workers in the past who had braces, (when they were working with me), did not seem to wear their retainers for very long after their braces came off. I do not know if they were slacking or if they had bonded ones put in.