Not that bad UNLESS you want to use points from both memberships to pay for the same night at 7 months. (Can't do it online). Otherwise, you just need to manage two banking deadlines.and keep track of point status (banked, borrowed, holding, reservation, transferred etc.) separately, by membership. Waitlists would also need to be managed separately by membership.
To combine points from both memberships, you either have to transfer points and call MS to use the transferred points, or you can also book some nights from one membership and the rest from the other. Then you have to either call, chat with or email MS to link the nights so that you don't need to change rooms in between.
Technically, transfers between memberships are one per use year per membership, but MS has been known to waive that rule if the memberships are owned by the same person(s).
FWIW, I prefer the same use year for ease of use (and fewer online glitches when IT updates), UNLESS you plan to use each membership separately. For example, use OKW for summer vacations and BCV for F&W vacations, or maybe stay at OKW one year and BCV the next, using banking and borrowing.