I tried the one girl after the other back in the late 90's. There was a half hour drive between the 2 girls. It was an interesting experience as a one off experiment but I wouldn't and haven't repeated it since. I had seen both girls before and I booked the second girl after leaving the first one, so it wasn't pre-planned. On that day I would have extended the time with the first girl but she had something on and I was still in the mood for more. Back then I also had very limited time slots when I could punt so it was either go for number 2 or leave it a week.