[LHaven]

Try zero days ahead. We don't camp any other way on extended trips, and by and large, it has practically never been a problem.

We took a seven-week trip in September to make a HS reunion in New England. We take it on faith that we may get detoured from our planned route, we may experience mechanical, medical, or pet problems that delay us, and so we won't be able to predict our arrival date with any certainty. We just built in a cushion of time to get there, and don't reserve anything until we're close.

Each day, we decide how long we want to drive, how far that will take us, get on the smartphone apps, look up a campground along our route at about that target distance, and call for a transient slot for that night. If (as rarely happens) we strike out, we try a campground a little closer or further. Only once in 20 years have we crapped out and had to resort to a night at Walmart.

Occasionally, you discover the town you targeted is having a local event and is full up; then you adapt or divert your route. But even the misses can be happy adventures.

When we got to New England, the campground I had tentatively chosen for our two-week stay couldn't accommodate us. We found another that was just delightful, had much less of a stick up its backside, and we had it mostly to ourselves on all the weekdays.

On our way south, the South Carolina state park we had targeted was having some sort of event and was full up. We diverted to a more obscure state park and discovered it was a retriever training facility, complete with large running meadows, lakes, marshes, and stables (image). Our two furballs were so overjoyed to get a "trip to dog disneyland" that we stayed an extra day.

On the way back home, a local fishing tournament in a central Texas town left only a couple slots open at a park we'd never heard of. It was a lovely place, right on the North Llano river ("dog Riviera"), with herds of deer running around the margins, so again we stayed an extra day.

I realize one has to have a very flexible deadline to enjoy a trip this way, but even when there are deadlines, as long as you have planned an achievable schedule with a bit of cushion built in, choosing your campgrounds on the fly adds a surprisingly negligible amount of risk to your plans.