....one bit to consider, if even logistically possible for you, is to p/u and return tanks yourself. the O2 shop i used thought it amusing but appreciated. one phone call and i would have all my tanks in a rack waiting for me on arrival...quick switch out and on my way. this would also allow me to pop my head in the back room and chat/thank the techs. they usually don't see their clients, and i have always believed a face to the name is a game changer...once was handed an m60 regulator, no charge, with "use as long as you need" ...i still have it........