I lasted about an hour. But that was with spider tickling. If it was the fast, intense tickling like what you see in clips, or read in stories, I'd probably last five minutes, and that's being optimistic about it.
i'm very ticklish so i cant be tickled for very long without breaks in between. However it can last all day as long as whoever is tickling me can let me rest after 5 straight minutes rest then continue for another 5 etc