We host occasionally with Airbnb, so I just looked up the scheduling settings. I needed to check in anyway, so this was a good reminder. There is a pulldown menu that lets you choose how far in advance to make your place available--- 24 months, 12 months, 9 months, 6 months, 3 months, and unavailable by default unless specifically selected.
Since we only host for a handful of weekends, I set it to unavailable and then select dates whenever the football and graduation schedule (college town) is available. Most local hotels get filled a year in advance, so people looking on Airbnb get frustrated that no place is available, when in actuality, the hosts just haven't opened their calendars for booking yet. I think a lot of people here set it for 6 months ahead.