According to at least one dentist, doing the huge sugar-fest all at once is better for their teeth than spreading out the sugar snacks over a longer span.
My kids have very soft teeth (in general), and we've always tried to keep the sugar to a minimum. But yeah, we did spread the candy out over a month. But we tended to have it as dessert, which would have happened anyway (it would have just been something else).
Still, the whole sugar fest isn't high on our priority list due to the fructose malabsorption (sucrose is 1 fructose molecule with 1 glucose molecule - and since the sucrose is broken down in the gut to be absorbed separately, it counts toward the total load per day they can tolerate). So we have other strategies, like buying the worst of the candy off them. No gummy candy for anyone (serious tooth wreckers), and no red dye for Mr B, and no chocolate for Miss M, and no fructose, and ... they usually end up with a few items they can eat, and a couple handfuls of change. So far, it works for us.