Ok you are talking a small supply then. You need to get some gas stabilizer to keep the gas fresh.
Make sure you vent that van if you store it inside of the van. I live in the country so I can store regular gas in cans under shade on the side of my property.
I think non-ethanol gas last longer.
If want an emergency supply I fill my old Jeep tank up with gas. That Jeep is not driven a lot compare to my other Jeeps.. Just easy to store it there.
You might want to start a new tread on how to store gas. There might be some safety issue I have not consider.
I actually used two years old gasoline in a modern car engine and it was just great. I also use some from the drums right now and then replace it with a recently bought at gas staition too.