I'm surprised that nobody has mentioned a good article by John Farley in this month's Flyer. He talks about this issue - with a good example of a time when he was making a large number of very short Harrier flights (typically one or two minutes, IIRC - maybe 15 minutes of log time in 10 sorties
). Total time wasn't close to the 15 hours a month that he was supposed to have on type, but those short flights contained some very demanding flying. Worth reading