I used to use the RV Anti-freeze in the water lines (as well as drains) but, at least for me, it leaves a nasty tasting residue when using the water. Even after sanitizing it with bleach water. It "Lessened" the taste but it's still there. This year, I decided to blow out the lines. Doing this made it CLEAR to me that it is NOT good enough to just "Drain" the tanks and open the valves. There is so much water left in the lines even after everything is drained that most folks don't realize.
So whether you blow out the lines or put anti-freeze in them (or both) you are better off doing it if you get winter with freezing temperatures. (I guess if you live in southern Florida this probably isn't a problem but here in NE Pennsylvania, it's definitely a concern.)
We also go to WDW and the fort after we winterized, so we have to "De-Winterize" it and "Re-Winterize" it upon return. It's a bit of a pain but I still go through the effort because it's much less of a pain then trying to replace the plumbing.