Since you are talking about boondocking, you'll want to bring the batteries back to 90% when running the genny. Letting the battery voltage drop below 12.00Vdc(50% charge state) will shorten the life of the battery.
Here is a 12v battery voltage State of Charge chart:
12.6+ = 100%
12.50 = 90%
12.42 = 80%
12.32 = 70%
12.20 = 60%
12.06 = 50%11.90 = 40%
11.75 = 30%
11.58 = 20%11.31 = 10%
10.5 = 0%When using the batteries under these conditions, check the electrolyte levels frequently. Be sure to use distilled water to refill the levels. Minerals in tap/well water will shorten the life as well.
Check out this
12vdc Voltage Meter to keep an eye on your battery state of charge.