On one particular road trip where we were in a new place each evening it finally occurred to me around night 5 that it was really stupid for me to be schlepping a suitcase full of things that were A. dirty, B. not going to be used/worn in the next 24 hours, or C. both. Since that time, my methods of packing for road trips has totally changed.
In the back of my van (or car trunk in the pre-van days) I put a laundry basket with clean clothes and a clothes bag for dirty clothes. (When my kids were little I would take it a step further and put outfits together into gallon-sized bags so they were already in sets.) Toiletries go in a small case which is then put into my daypack. Books, sketchpads, and other hobby type items go into their own bag. Shoes go into a tote bag. Basically my trunk area becomes a closet. At each stop I grab the items I want for that night or next day, toss them into the daypack, and leave the rest. On the rare occasion that I want something left behind it’s not usually that big of a deal to just pop down to the car. When I know that we’ll be arriving at our next stop late I just pack up the daypack for the coming evening when I return to the car in the morning.
This has also worked really well for camping. Instead of having all of my clothes in the tent to get tromped on or wet when the rain fly fails, the majority were stowed neatly in the weather-proof car.