Probably thousands where I know all the words if someone ELSE is singing them, but far fewer where I would be able to sing the whole song, in the right order, from memory. But I don't sing professionally, just do the occasional floor spot at clubs, and sing in sessions, with or without words in front of me. I do like to keep doing different songs, maybe to fit the occasion, time of year or whatever, which may mean that my aging brain does not retain all the words from one year to the next. But I am really trying to do more without crib sheets!