If you are booking home resort at exactly 11- months out from date of arrival, or another resort exactly 7-months out, you can book only up to 7 nights. You can add nights in the days thereafter via modifying the reservation.
The online computer system actually has a maximum of 30 days you can book at once, if you are doing the reservation well past the 11/7 window, e.g. if you go online at nine months out, you can book up to 30-days at once online At home resort You could book more than that by calling MS rather than using the online system. The actual limit to how long you can make one reservation is the number of points you have to do it.
Some have incorrectly mentioned that there is a 30-day limit because being able to do more could allow you to claim residency in the state. That is not true, including because the POS documents declare that members cannot use reserved time at a
DVC Resort to claim residency.