We've made several 2+ month trips in our B Sprinter. Usually we are sightseeing and touring for 5,000+ miles, but sometimes we stay somewhere for a week or longer just to relax.
You can be very nimble and light on your feet in a B van. It's tailor-made for exploring back roads or small villages (such as coastal Maine) without worrying about getting stuck and unable to maneuver out.
No problems with campsite size, and you aren't limited to full hookups or 50 amp. Very fast setup at a campsite or departure. You sightsee as you travel from location to location, with all your clothes, shoes, jackets, bathing suits, towels, snacks, medications, foods and comforts right at hand. Easy to park at attractions and grocery stores.
After the first year, we started removing all the "essentials" we thought we needed to haul around, and soon had more than enough space. There's plenty of room for clothes, and we do laundry at campgrounds once a week. We also use campground showers most of the time, and buy groceries about every four days. We mostly prepare meals, but eat out about once a week, often at lunchtime.
I thought the small size of the holding tanks would be an issue but it's not for us. We take on fresh water as needed and dump the tanks about every four days.
We have a propane generator, and have never had trouble finding refill stations. Comes in handy if you are dry camping. Our fridge is three-way. Operate it plugged in to campground power, run it on propane, or power it via 12-volt as you drive the highway.
We use the van as our car and do not tow anything. Once when we used a relative's extra car, it was more trouble than it was worth to pick it up and get it back.
A B van is ideal for long haul trips for the fuel economy and other savings. For example, if you want to visit Newfoundland, a B might cost $500 round trip on the ferry versus double or more for a big RV and separate vehicle.