There are some times of the year that calling every day is not needed. August is one of those times.
I, who only stays in Grand Villas, would call the first day, I would ask if I could reserve five Grand villas for the previous two weeks, if they say 'yes', calling every day won't be needed. I would reserve the one day of my vacation that I could.
If the answer was 'yes', I would call on the third day, ask the same question about reserving five grand villas for the previous two weeks, if the answer was 'yes' again, I would reserve the next two days that I could and I would call next on Friday of that week. I would also call Monday, ask the same five GV question again, if 'yes', I probably wouldn't call again till Friday of that week or the end of my vacation, whichever came first.
Every day calls are not needed in all seasons. If they said, which they have, "you could reserve twenty GVs for the last two weeks, I would not call back till the end of the vacation.