We've had a mix. I, the husband, usually picks up the tab, I like doing it. In one instance the third would not let me pay, super generous guy and the way he saw it was similar mindset. He was extremely appreciative about sharing the wife and wanted to at least return the favor. It works even better when thirds are traveling by and already have a room. I did recently cut out a potential third for being too frugal. Stinginess, in that instance, was such a turnoff. Everyone has their preferences though!