I am also calling day to day to book a SV at BWV for next Easter. Member Services told me its a good idea to do that because its a popular time. You could call and ask them if they think you should call day-by-day. Once I didn't call until 3:00 pm, and they only had one SV left.
Next year, Easter is March 27, and this is right in the middle of spring break time. I'm assuming it will be packed.