If you want it to last a week you have to learn how to save water. The greatest saver we found was how to use the water heater when taking showers. We turn the water heater on when getting ready to take showers and turn it off when the water gets warm. Then we only have to use the hot water for the shower, no trying to mix it with cold to try to get the right temp.
We can last 7 days.
Most RV batteries live a long and useful life, some are murdered.
2000 National Sea Breeze F53
1998 CRV Toad