it's a hassle.
if you buy 2 contracts under the same member number (titled the same and with the same UY month), they would function as one contract (at least at the 7 month window since you are looking at different resorts.) you could pool pts from both to book a single night at SSR at the 7 month window, for example.
with 2 UYs, you have 2 separate contracts with separate banking windows. so it's more to keep track of, for one.
if you want to book 4 nights with SSR pts plus 2 nights with your BWV contract, you would have to rely on MS to link 2 separate reservations so you wouldn't have to move. if you wanted to book a 7th night by combining pts from both contracts, you can't do it without a transfer.
if you transfer, you would technically use up both contracts' once-per-year transfer. also, remember that transferred pts cannot be borrowed, so that can limit how you can use the transferred pts.
having 2 UY months can be done, but it's definitely more to keep track of...
(keep in mind that you can never combine SSR pts and BWV pts during the home resort window at 11 months out - regardless of whether the UY is the same or not.)