We have a 25ft 5th that has about the same power requirements and battery system that you have, but a PD9260 mounted right next to the battery compartment.
We can go 3 to 4 days on a full battery charge. We have solar; and can go pretty much indefinately (occasional gen run in winter). Before we added the solar, the 9260 would easily bring the battery to 90% in a 3 hour run after 3 or 4 days.
I'd get a new converter (PD92XX is my choice), mounted within a few feet of the battery. Get some way of measuring your voltage and current use (some pretty basic metering is all you need; a cheep plug in voltmeter at minimum). Use your present battery, and try it for a 2 week trip.
Unless you're using more power than you described, I suspect you can go 4 days at a clip with your present battery.
Not going below 50% is a nice rule of thumb, but a couple of times a year going down to 30% is not going to kill a battery. My no-name GC's are 9 years old, and still going strong.
Doug
