Planning at 11 months out really isn't all that difficult bad for us, as we're currently "planning" trips for 2012, 13, 14, 15 & 16 (both Disney and not), in addition to all of the ones we actually have reservations for yet this year and early next, and those that we don't yet have for later in 2011 but will have in the not too distant future. (We're pretty much long term planners - always have been. Started as a kid when my folks would get up from the Christmas Eve dinner table and proceed to decide who's house we'd be at the next Christmas Eve, and so on. Then repeated when we got married and started doing the exact same thing).
As far as the actual "details" that go into any individual trip or reservation (activities, dining reservations, yada yada) - those don't need to be dealt with until 6 months or less prior unless we're travleing with family members who need more lead time to actually commit to a trip.