Have been there, done that, not commercially, but for me to call a mayday the wing would have to be falling off or in a S/E I'd be calling it only if I knew that the outcome was going to be bad and I was going to crash and not be able to tell my story later. If I was out in the open and thought that there was a good chance of survival, depending on how long I've got left to prepare for the landing I probably might not bother.