For my family of 5, we go about 6 days without having to refill water or dump tanks if we can use the campground showers. We do the dump/refill using a blue tote and a similar fresh water tank and aquarium pump run from a small inverter. If we have to shower in the trailer we can only go a couple days.
For power we have solar panels so it depends on the sun, tree cover, and whether or not we need to run the furnace. Since we usually camp in the woods (not so great for solar, but we still get some) and have 2 110AH 6V batteries, usually around 10 days without running the furnace, and 3 days if we do have to run the furnace. There are a lot of factors that go into this one though - we have LED lighting, are a pretty conservation-minded family, and use the furnace as little as possible if we need it.