Two summers ago I arrived at G V mid day the week before Labor Day not expecting the DW to come back with one of the 36 electric sites. Moved to South Lake Tahoe on Labor Day and got into the city CG after lunch without a reservation. Am I that lucky as I almost always get into where I want to stay without a reservation??? I like the USFS CGs that do not take reservations BUT do not show up Friday. Thankfully even on Monday of Labor Day many of the working folks had to leave Tahoe to get back to work.
The freedom of No Reservations makes the occasional not getting in not that big of a deal. Being fully self contained makes going without reservations much easier and one of my favorite fallback options is a local small airport.