I've owned fifth wheels for 7 years and I never drain the water heater until it is time to winterize it. The water won't go bad. There have been times when the trailer wasn't used for six weeks.
After you break camp and disconnect from your water supply or, if boondocking and turned off the water pump, just open a faucet to relieve the pressure and then close the faucet.
Don't make camping a chore.
Bob and Joyce
2013 CC Silverback 29RL
2010 Ford F250 XL Crew Cab 6.4 liter diesel
ATU Local 788