Keep in mind that things like the water heater igniter, reefer igniter, water pump, heater and interior lights are all 12v. Your outlets, micro, and AC are 120v.
I changed my trailer batteries to 6v golf cart batteries in series and changed most of my interior lights to LED and the difference was dramatic as far as run time. I have an on board Onan 4kw gen and run it to use the micro, make coffee and toast but otherwise only run about every 3 days to recharge the batteries.
You may need to use an inverter to power your o2 concentrator which will necessitate the use of the generator to recharge the batteries a little more frequently. You will develop you own routine as you spend more time with your trailer and learn the ins and outs of it's performance.
