I am not a big fan of this rule, either, since we usually go for 8-10 days. But, if you do reserve 7 nights right at the 11 month mark, your chosen room is effectively taken out of the inventory for those seven nights. No one else can book that room until day 8. You can simply call back within those 7 days and add on the number of additional days needed without losing that room.
Of course, you can book 8 nights at 10 months and 29 days, 9 nights at 10 months and 28 days, etc. For most room types during most of the year, waiting a few days would work.