I am assuming you mean you have contracts with different use years because if they are the same use year, they should be under the same master contract and thus considered as one. With two use years, you can either transfer points from one to other before making the reservation, although already banked or borrowed points cannot be transferred, and then make the reservation 7 months out at 9 a.m. eastern or after by calling MS because you cannot do an online reservation using transfered points from a different use year. In the transfer situation you can use points from both contracts for any night. Alternatively., you can make two different reservations one for some nights using one of the use years, and the other for the rest of the nights using the second use year, and thereafter ask MS to link the reservations, which results in not having to change rooms. Though you can do the two ressies on line, they each have a separate start date when made and thus, for example, you might reserve the first six nights at 7 months out with one use year, and then 6 days later reserve the last four nights with the other use year. If using that method you cannot combine points from one use year with another use year to book any single night.
As to being able to reserve 7 months out, Aulani is usually hit or miss in Sep and for island garden view studios, it is more miss than otherwise. Moreover, you are likely to have issues booking 10 nights in a row in any studio. Thus, do not be surprised if you need to wait list and hope it comes through..
