If there is a low spot in the plumbing, water will sit there and freeze. You have to make the decision as to whether spending the fuel and time is worth your peace of mind and to prevent possible damage.
As an aside, I used to blow the lines out. Then I bought a small "emergency sump pump". I bought a short drinking rated hose, stick the pump down in a bucket and keep the bucket full of RV anti-freeze while I pump it through all the lines in the trailer.
Since it is under pressure, I can push anti-freeze all throughout the plumbing. Every line, valve, low spot, ie: anywhere water can sit will have anti-freeze. I am glad I did as it got to 20 below 0 F. here last winter.
The pressure is not so high as to damage the plumbing, but it lets you run anti-freeze through everywhere you can hook a hose.
I even use the pump to push RV anti-freeze into my power washer valves and hose/nozzle, etc.
Of course, I ran some bleach water through the pump before using it the first time and sanitize it yearly.
psssttt drcook = David R, not Dr. but thanks for the compliment. Most folks just call me Dave.
2004.5 Chevy Duramax crew cab 4x4
2010 Crossroads Cruiser 30QBX
1991 K2500 4x4 being restored