We have a gas only water heater. I used to just leave it on all the time, as it was usually our family of 4 and multiple other families... never knew when someone wanted to wash something, or use the outside shower, and multiple showers at night.
Now that it is usually just wife and I we just turn on the water heater when we need it. As others have said, about 1/2 hour before dinner. Gives us all the hot water we need for dishes and showers. Then I usually shut it off when we go to bed.
Our water heater is well insulated, but still turns on every couple hours (sometimes sooner) to maintain temperature.
If camping with whole family or friends, sure, keep it on. Nothing to do with being able to afford the propane or not, I just don't see the need to heat water during the day when we simply don't need it.
