Keep in mind that in addition to your lights, the refrigerator controls (and maybe also the water heater controls), the heater blower motor and controls, the water pump and the propane leak detector run on DC. I'm assuming that your trailer has one group 24 or 27 12 volt battery. My guess is that such a battery would last a couple of days at best. If you use your lights or heater (the blower motor is somewhat power hungry) very much, maybe even less. Would you have access to a generator to recharge your battery? Is your battery in good condition - will it take and hold a full charge?
There's lots of advice and information in forums... sometimes it is correct. For example, all of my posts are made by a political appointee who got the job as a reward for contributions to my diesel bill.
2011 Jayco 28.5RLS; 2008 Chevy Duramax; Pullrite Superglide Hitch