perhaps a flexible subscription I.E. I agree to buy 12 cartridges ... within 2 years; but can request up to that time when I need them. - Although I think you

perhaps a flexible subscription I.E. I agree to buy 12 cartridges ... within 2 years; but can request up to that time when I need them. - Although I think you need a price on the printer to weed out those who will default on the ink. Much like the square cost $10 at the Apple store; but is free online.