I use the AirSep Free Style. It lasts about 2.5 hours and has an extra battery for about 2.5 more (on 2 liters). It also comes with a car charger, and AC adaptor, so it makes it easy to travel with. It weighs abound 4 lbs.

Air Sep focus are pretty good. I use on long airline flights

I use the Simplygo for work (plug in or battery), and I too find it cumbersome to lift or drag around and you're right, the batteries last for 2-2.5 hours and they are done...I have the cylinders too for portability, and they don't last long either...during the night i use the electric home concentrator, loud but works...as for charging, they are pretty quick..but God help us if we lose power for more than 5 hrs., (my big cylinder would die) ... SO just make sure what ever units you are using are topped off with power to go....

These only go to 2 lpm continuous. Sorry, don't know about others.

No I need continuous unfortunately