Hello,
I had a few times punt with girls asking me this question. While it make sense when I taking a bit too long and time is running up, it does make much less sense when the girl ask for that after 10 min when I booked for 30 min.
I usually say I booked for 30 min but some girl object they don't want to do sex for 30 min (although I may have just started 10 min ago). Worse are the ones who don't understand english and I don't even know what to say.
What do you do when the girl ask this question?