in my early days of punting I never used to walk and always felt obliged to stay and have had some bad punts because of it, now, with experience, I always go on the vibes I get from the girl when she opens the door and as I am walking in, if the interaction is fun, flirty and she comes across as someone I want to spend the time and money with I'll stay, If it's a frosty reception, hard to chat because of Language barrier or she seems put out after a hard day I'll just say sorry I changed my mind and I'll walk.
The last time I walked was because the girl I had booked was busy, I had booked at midday for 9pm, already had to wait an hour as she was busy, when I finally managed to enter the flat, the booked girl was still busy, her flatmate was there, pretty girl, but it was hard to try and discuss what I was looking for, it was hard work and I just didn't get the good vibes so I apologised, shook her hand and left.
Punting is like any other transaction, if your not happy with what is offered just walk away