I like to take my time. Anywhere from 10-30 minutes usually. Sometimes I just know I'm only going to get one shot in so I might time it for 40+. It would go something like BBBJ, DATY, FS, DATY, BBBJ, finish.
My numbers are skewed as I haven't gone more than 3 days without sex this past month and a bit. If I had to guess an exact average number I would say 17 minutes of sucking and fucking without taking time out to DATY, DFK etc.