Bob- solenoid is energized on the two small studs to connect, and to stay connected. Lose chassis voltage and the solenoid drops off, also if chassis batt voltage drops as Scott says, Vansco will disconnect the solenoid.
I think you have other draws on the chassis batt's regardless of the solenoid being connected or not. I do, and mine is abour 1.4A IIRC (I tracked it once but not sure I recall the actual parasitic draw off top of my head).
Baja-tested '08 2-slide 36'
Alpine: The Ultimate DIY'er Project