Is BCV your home resort? If so and you plan to call at 11 months, I don't think you need to call day by day unless you want to be absolutely sure of getting a dedicated two bedroom unit with two queens in the second bedroom. For anything else, one call should do it if you are calling when your 11 month window opens.
If BCV is not your home resort and you have to use the 7 month window, then yes, I think you should call day by day. You may have to waitlist for some or all of your days.
I don't know if it's necessary, but I book day by day at 11 months. I know it's probably not a big deal, but I just wanted to be reassured. Also, I can never wait for the day to book all of it, I'm too excited.
However as the PP had mentioned, if you are calling at the 7 month window, I would definitely call day by day.