The biggest problem is combining points at 7 months. If you need points for a stay from both contracts, you cannot do that online: first you have to call Member Services to transfer points. Those will not appear online even if transfered before the 7 months window opens, so you have to call MS to book using transfered points. This means you'll be able to book only after 9am, while people who can book online can do so at 8am. This hour difference can be a problem for busy times.
At 11 months it is less of a problem, so if you have two contracts that you intend to use mostly for home resort bookings, the only small hassle is managing the points from two different contracts, with two different banking deadline (and the potential for problems with transfered points).