Two wheels is enough.
The ride itself was Nashville to Ocean City MD, then Hwy 50 to Sacramento CA and back to Nashville. I went with the understanding "I don't know how many 500 mi days I can string together". As it turns out I managed a total of 1893 mi in 5 days (A strict schedule as working people have to get back to work).
Spark plugs: easy and cheap. I thought about Iridiums, but the standard plug works fine and I got the new ones at a local auto part store.
Oil: The first time I've changed my own. Got some of the recommended Shell oil and K&N filter. Not too bad; cleaned the screen also which means getting the exhaust disconnected. My Scrambler has never lost, burnt, or dripped a drop of oil. I've owned a lot of air cooled bikes, and cannot say the same for the others.
Chain: at 12000 mi the original chain had several miles left in it, but I've made a mistake of expecting too much of a chain on a long trip. Installed an EK and a new drive sprocket. Ran perfect and smooth.
I bought an aux 1.75 ga tank and carried extra gas but didn't make it to where lack of services was expected. I didn't weigh the gear, but it wasn't light.
It rained 3 days out of 5. Real gushing, standing in the road, cars pulled over rain in Virginia. The Scrambler wasn't phased at all. We only stopped to put on rain gear and then motored through weather as it was. The AV55/AV56 Avon tires never twitched over wet tar snakes and wet washboard pavement in West Virginia and were predictable and competent in all cases. The Scrambler consistently gave 55mpg whether going 5+ on I-40 and I-81 or winding through Maryland and West Virginia back country at a brisk pace.
The ride was great fun, but I knew at the end of a long 500 mi day that I needed rest. The next planned day was 550 mi. The Scrambler would easily do it, but the old man couldn't so I said farewells and headed to the house.