Thanks, everyone! Sounds like planning ahead is key.
I guess I should say that another concern I have, aside from just breaking up long drives (and we don't plan on terribly long days....we're making tentative plans for a 3 1/2 week trip next summer, and the longest driving day as it stands now is 7 hours, and that's to get home on the last day....but with a 3 year old even 4 or 5 hours can seem like forever :)).....is when there's something we want to stop and see along the way but we can't or don't want to devote an overnight stop to it.
One example (the one that prompted me to start the thread) is a day on next year's itinerary where we're planning to drive from Greensboro, NC to Charlottesville, VA...the total drive is only 180 miles, so maybe a little over 3 hours. But we'd love to stop and see Appomattox Court House on the way (about an hour from Charlottesville). In just a car, it'd be a no brainer; perfect place to stop for a couple of hours, have a picnic, kids could get a Junior Ranger badge, etc. But I'm worried it won't be nearly so reasonable with the trailer....the website says they have bus parking for groups, but I don't know if they like to give out their bus parking to people who just have vehicles the same SIZE as a bus but with just 6 people in them. I know we'll have to adjust how we travel somewhat; I guess I'm just trying to get a feel for how many things like that it's reasonable to still expect to be able to do.
