Thinking about it more, you could avoid using the inverter a lot of the time with these couple items:
Cigarette Lighter Ports with switch:
https://www.amazon.com/ONLINE-LED-ST.../dp/B00PXAN1DU
Car Laptop Charger:
https://www.amazon.com/Outtag-Univer.../dp/B071SDW4QG
You'd probably want to go for a battery monitor like Captain mentioned, and find one with a low voltage cutoff so you wouldn't risk running the batteries dead by leaving something on.
Converting from DC to AC back to DC is not very efficient, especially when the DC to AC part is designed for high current and you just need an amp here or there a lot of the time. The laptop puck also has USB outputs, which could charge your phone.
I also noticed they have fans and a range of small coolers/refrigerators designed for cars, so you'd have a lot of accessory options. You might already have some things from your van living days, but if not, they could be useful the next time you travel.