I did the same with my two lockoff weeks, split into 4 weeks in a row, at Beach Place for 2006 mid Feb - that gets you weeks more than 13 months ahead. Recently did it for my two July 4 weeks at Manor Club 2006 which I usually exchange to get bonus weeks, or rent one of them. The other Manor Club week I own will be turned in for points. I've never had problems getting exactly what I wanted with multiple week bookings like this.
On the other hand, because I could only book it 12 months ahead, I had a terrible time booking my 1 week (split lockoff) at Canyon Villas for 2006 - took me 3 weeks to get a suitable week on the stupid new Marriott reservation system.
Brian