How many make park reservations vs find as you go.

We have traveled for many years, including a two-month ocean to ocean trip back when my children were young. We very rarely reserve a site. The exceptions are Labor Day weekend, Fourth of July, and Memorial Day. For those, we start planning about two weeks early as to the area we want to be. Then we call and make reservations that will carry us through the busy time. On a travel day, we call ahead about two-three hours if we are driving late in the day. Campgrounds start to fill up around 4-4:30.