Are you missing a lung?

Either you are pulling my chain or you might be the record holder for the least air consumption! At 90 feet, I doubt I would even get 45 minutes out of an 80 cubic foot cyl. You are saying you get 100 minutes with 1000 psi to spare, that does not compute to me.

Maybe I am missing something.

Now I have no idea what you are talking about "alyays sharing an octo", it is for an emergency, not for always use.