My minimum outcall is an hour, whether they live 5 miles away (I do have this according to my sat nav, but its a pokey little way to get there) or 25 miles away. Think about it this way, even though you prefer outcalls - which I also do, but to hotels - if you weren't on that, you could have done, for example, 2 x 30 mins. Or worked into 2 x 1 hr.
Now everyone works differently and (mostly for health reasons) I wouldn't have appointments running so closely together, but the point still stands about time I've set aside in the day for travelling, having this appointment, then travelling back, showering, touching up make up etc in time to be ready for another appointment. I love outcalls! But business wise, I won't offer refunds from a cold, business perspective - they can easily take up 2 hours, if not more, of my day. In that hour I'm not potentially having sex/being sexy/doing sexytime because I'm driving, I could be answering calls, emails, or having more sexytime and making more money. Business is business.
So as much as I might like a person - and I do have plenty of clients I genuinely do think are pretty sound blokes - you've bought my time for X period. If you want to leave, or for me to leave before that time, that's your decision to make - you're a grown man. I'll happily stay for that time; I'll continue to be sexual with you, or we can sit and chat, laugh, do whatever really. There's plenty of times I've found bookings have overran by 5-10 mins just by chatting and laughing with some clients. But if you look at your own watch and call it a day, well, I'll remind you that you have X amount of time left, or more likely that it's only... If you still want to leave, that's your call. Without being blunt, I don't recall ever getting a part refund on anything else I bought and used part of.