I have winterized many RVs this way and I never quite get ALL of the gurgling out of the lines. There is always trace water somewhere. If you are draining your hot water heater and blowing out the lines with decent air pressure (as mentioned above) you should be fine. I would add that I always leave any faucet open throughout the winter, and I relieve pressure at the water pump by disconnecting the line on one side or the other. Mine (and most I've seen) have quick connects there so I usually just leave it unhooked there for winter as well.
If your unit has an RV toilet, make SURE to get it completely cleaned out though. The valves in RV toilets are extremely fragile and are usually the first thing to freeze. They are about $50 bucks. Ask me how I know.
I'm not sure if SMBs are plumbed with PEX, but the stuff is pretty impressive, and with brass fittings you probably would never bust a line anyway unless you left the system fully pressurized.