I am sure lots of actors and actresses hide medical conditions as far as they can to ensure they can still work . I think most would wish to shuffle off this mortal coil whilst they were still acting or performing on stage , a few , famously, Tommy Cooper and Sid James , got their wish others like Ken Dodd soldiered on way , way beyond the time they should have retired but they simply cannot bring themselves to step "out of the limelight" . The lucky few become National Treasures so however inferior their performance is compared with their hey days when they appear we still revere them .