At 11 months yes, you must use contract(s) with that home resort.
You are never allowed to "unborrow" points; once points are borrowed that's it; they remain in the Use Year they were borrowed to (and can NOT be banked either).
At 7 months ALL points [under your membership #] are treated as one big pool and you can (and I have) used them interchangeably for any of your contracts. For example, I've mixed things and used 3 points from my VGC contract and 49 from my BLT one on a single reservation made less than 7 months from arrival.
What some people do is take current use year points (2010 for example) from contract #1 and also borrow next year's points (2011) from that contract to make a reservation in 2010 at 11 months out. Assuming contract 2 has a different home resort, bank 2010 points for it and then in 2011 make a reservation at 11 months out using 2010 & 2011 points.
Hope that helps!
Thanks DVCGeek - I certainly have a better understanding of the system now. I'm assuming that if contract #1 and contract #2 are at the same resort and have the same UY that you could combine them at the 11 month mark so that we could buy smaller contracts so that maybe we could sell one later if we no longer had the need for as many points?
Maybe I'm too worried about the 11 month thing as well - we try to go when the crowds are low (typically end of April or early May). This year we went right before spring break crowds because of the new baby coming but at 7 months out will we still have a wide choice of 2BR villas if we're trying to go during the lower crowded times?