Two points have been mentioned here that need more discussion: life of the batteries connected in one parallel bank vs. two switched banks; and the length of the cables connected them leading to uneven charge.
Suppose you have two battery banks that could be connected either in parallel, or switched and used on alternated days (a typical scheme). They are 100 AH each, and each evening you use 50AH in your camper, recharging fully the next day. If they are connected in parallel, acting as a single 200 AH bank, the Depth of Discharge is 50/200 or 75% each night. According to manufacturers battery charts they would withstand about 2500 cycles till end of life (I used Lifeline's chart, but others are similar). If instead you switch between two 100 AH banks, each night you will discharge the one in use to 50/100 or 50% DOD. On the chart this gives 1000 cycles to end of life. However you are alternating between two banks, so for the system you get 2000 cycles. Therefore the life when used as two switched banks is 20% less than used as a single larger bank. As the Depth of Discharge increases, the difference will also increase because cycle life decreases non-linearly with DOD. It used to be common in boats (which are far more dependent on batteries than campers) to use two switched banks, but due to this lifetime calculation most boats now are wired as one large bank.
Regarding the wiring for two banks in parallel. It is common (but wrong) to wire the first bank positive and negative to the power bus, then wire the second bank to the first. Any voltage drop due to the charging current in the second bank will result in its charge being lower. In batteries charged for a long time compared to their discharge, the difference will be small, if charged quickly and for the shortest possible time it could be large.
The correct way to wire them is to run cables between the terminals of the two banks, then take the positive power bus cable to one bank, and the negative cable to the other. Since the current from either (and both) banks goes through these wires, any voltage drop due to them is seen by both battery banks and they will charge and discharge at the same rate (or at least, at rates not influenced by the wiring).
