Keeping your RV batteries alive takes a few steps to ensure they last as long as possible.
Make sure you never let the water go below the lead plates. Keep the water topped up to about 1/2 an inch above the lead plates. You can see them if you lift the battery cap and look down inside. Used distilled water. How often you need to check them depends on your usage, but generally speaking it is a good idea to look every month.
Make sure your RV batteries are getting enough charge, and often enough. A pair of 6 volt deep cycle like the Trojan T-105 RV batteries need about 20 amps of charge on a regular basis. Your RV charger can handle this when it is plugged in. If you are charging them with an independent charger, it needs to be a good one. The small table tops don't hurt, and can help go longer between full charging, but they won't do the job on their own.
Use them charge them, use them, charge them.
If you have an older rig consider unplugging after they are charged up. This prevents the batteries from being overcharged and boiled dry if the charger decides it doesn't know to shut off. This rarely happens in newer units. Keep the connections clean.
Give us a call with any and all RV battery questions, we always offer friendly advice and information.