The only advantage to owning at other resorts is to take advantage of the 11 month window.
But, you must own enough points to complete a stay. This can be accomplished with banking and borrowing so some buy a smaller contract for certain times of the year. So, if you really wanted VWL for an EOY Dec trip, you might by 50 points, and with banking/borrowing, would have 100 to use there at the 11 month window.
But if your wife LOVES BCV and has no real desire to stay elsewhere during really busy times, I don't think its necessary.
We own at BLT because MK is our favorite. We know we will stay there for at least part of every trip. If we want to trade to either BCV (which we are doing this summer) or VWL, we will take our chances at 7 months. But if it doesn't work out, I am okay with it.
Now, DH may decide after staying at BCV, that he wants both, just to guarantee some nights there every summer. If that is the case, then we will add on there instead of BLT next fall.