All of them, although my spouse tends toward being on the social side and under certain circumstances will keep the conversation going, well beyond what it's intent was originally. Especially if it's one of his interests. If it's one of mine, I can discuss things ad infinitum, but it happens very rarely. I tend toward now at least, creating pauses and silence, if it makes the other person nervous then I'll usually ask a question.
So yes, somehow I think that it's my job to maintain conversations in certain social settings, in my home, in restaurants, clubs, if people are there at my or my spouses behest. It seems that it is the job of the host or hostess to ensure that everyone has an interesting time.
I've also made plans for an evening out, and didn't want to go when the time came. Alone time is essential, my spouse used to require two days of it after a work week. I need that sort of thing as well, often, I would disappear at family and friends events for some time to myself and return later, or leave early.