Battery draining question

Our situation is similar to yours, in that we prefer batteries while camping (and no noisy generators). First thing I did was to figure out the amp draw of all my goodies. Then while conserving, tested my volts at the battery each day. We have 220 AH of power, and with not wanting the batteries to dip below 50% charge, we used about 8% every 24-hours (20 AH). So our 2 Trojan T105 batteries are drained down to about 50% after 6 days. And we have found that after 6 days, it's also time to refill the fresh water and dump the holding tanks. Sometimes we will plan a full hookup for a day to stock up and re-charge for another 6 days of dry campin.