No, never intentionally. I have ADD and dyslexia so I sometimes get the days and times mixed up and have unintentionally missed appointments. Three times with my p-doc, once with my t. I felt terrible for wasting their time due to the accidental mistakes. If I did it intentionally, I'd feel even worse. Besides, to do it as a test wouldn't be worth the stress and worry it would cause me. As others have said, it would just make going back a heck of a lot harder.