Traveling in a van for a couple years to see the countryside is my retirement dream and it’s getting really close, so excited!
But gone are the days when i can perch on some little wooden slat and not have my back flare up! 
Any advice/recommendations from older folks on comfort and ergonomics for mattresses and seating (and i plan to have a partition so swivel seats is not an option).
Thanks so much.
We went with 9” of high density memory foam for our mattress cut in 3” layers for easier handling, custom cutting and cost, basically three 3” toppers. Our drivers seat was getting a little soft and lumpy from time so I had that reupholstered with a firmer foam. While on the road, an electric heating pad for driver or passenger seat powered by a pure sine wave inverter.
I use comfortable fully mesh camping chairs for many years camping or staying in a rental and refuse to use anything else