I have a few hundred miles on my marathon supremes and love them. I mounted them in 30 minutes with a floor pump and stans sealant. I plan on running them on Pacific coast tour in may. You should alway use sealant with tubeless tires, it almost eliminates flats. I carry a couple tubes for the unlikely event you puncture tire in a way sealant will not seal. I will also cary folded used tire in case tire is damaged to the point it is unridable, both of which I would do even if I was riding on clinchers with tubes. IMO tubeless is the way to go.
I guess I don't understand the allure of touring with a tire that requires a floor pump and 30 minutes to mount...especially when you'll be carrying spare tubes and a tire anyway. How many flats are you getting? Excluding the first solo tour I did back in the late 70's (a flat tire disaster), I can recall only a small number of flats (less than 5) between my wife and I. This includes on and off road, fully loaded tours around the globe.