I think that is the key to it — when you meet someone for an hour there is only so much you can fit into in. Introductions, showers, chat and fun. The time flies by and even if you are not totally compatible you can still have a good time.
But 12 hours in the company of someone who you are not totally compatible with is a different story. As I said, if I was in the position to go for an overnight booking I know exactly who I'd like to do it with — while we have never been stuck for anything to say to each other I have spent time with here where we didn't have to talk and it was just as good, her eyes said it all! That's a sign of good compatibility IMO
It is interesting you say all your overnights were outcalls — I can see the sense in that.