My mom uses an Imogen One, it's about 3 years old. Weighs probably 3-4 pounds. On 2 liters of service, the battery lasts about 6 hours. On 3 liters, about 4 hours. It's been really good for her. She has a spare big battery, plus a spare half-size one. Recharges about anywhere there's an outlet, even in the car as we drive. She flies to and from AZ each year with it and gets along well. I think a lot of it is what you decide to be grateful for. Dad was on tanks at the last year or so of his life, and the portable has been a big upgrade over what he had.