On our new TT only drain it when I winterize, although I do open the low point drains if it is going to sit for a couple weeks. Our old hybrid had a drain valve built into the anoid rod, so I would drain that WH if it was going to sit for more than 2 weeks. Once I have to replace the rod in our new TT I will try to get one with the built in drain, just because...
TT-2013 Passport 3220BH
TV-2004 F150 FX4, not exactly stock...
with 2001 Kodiak K215: 2010-10, 2011-12
with 2012 Grey Wolf 26BH: 2012-19, 2013-24, 2014-11, 2015-6
with 2013 Passport: 2015-13, 2016-15 booked