IMHO, it would seem that if you use lots of hot water, keeping a good replacement flow through the tank, and have a good filter, you would not need to drain unless there is a problem. However, if you don't use that much HW, even with no possible freezing, it could become stagnant, for lack of a better word, and possible odors occur. In that case, personally I would drain and refill maybe once every month or two. JMHO
2003 Ford F-350 V-10 Crew Cab 4WD Long Bed
2004 Jayco Designer Medallion 29 RLTS 5th wheel
Bill, Gayle, and Mindi (dachshund)
Retired at last !
Nothing is foolproof to a sufficiently talented fool.