I personally ignore these enquiries.
Not because I don’t think they can do it, because sometimes they can. But when they can’t, it’s a really awkward end to the booking. Sometimes they’re reluctant to leave and start begging for extra time whilst furiously tugging at themselves. Not fun when they start sweating either, trying to squeeze another one out for the pure sake of it. I would honestly rather pace my booking out, with one longer slow round than 2 rushed stressful rounds.
That being said, some really do have hair triggers and I won’t turn them down if they have plenty of time left. But if it’s taken them a considerable amount of time and effort to finish once and there’s only a quarter of the booking left? Then absolutely not.