Well, the idea of "low point drains" sounds nice, but I just had my first casualty...
I always drain the trailer at low point drains. Usually I leave them open from where I camp last, to let the trailer rattle the water out of all the horizontal parts. I didn't do this last time, it's been sitting (level) in my drive way, and that's where I drained the water before it got cold last time.
The shower facet broke - there's a tube that runs between the hot and cold valves and forms a "T", with the other end going to the shower hose. That "T" piece broke. I'm guessing there was just enough water left in this horizontal pipe to not drain fully.
Fortunately this is a very easy repair, with plenty of room to do it, at least in my 2619. Cost was about $20 for a new facet at Camping World.
But that makes me think the winterizing procedure I've been using is inadequate. So I think I'm going to start blowing out the lines with air (maybe 40 PSI?). It'll give me an excuse to buy a bigger air compressor someday.
I just thought I'd post my rambling post in the event that someone else might be considering winterizing procedures for these TMs.