Leaving fridge on permanently

Unless you driving for a fair while each day the battery won't cope.

I charge my aux battery at night with a 3 stage charger that I connect to the andersen plug on the back of my car (I hook the cable to the garage door so I can't forget to unplug it before driving off.

Joe,
I agree with Nigel about the need to keep a charger on the Deep Cycle batt when possible.
I have a ARB (ie: Engel) 40 litre fridge on a slide permanently in my Patrol. I keep it running 24/7 for no reason other than to keep a few bottles of water and stubbies etc. Then it's ready whenever we go camping or a day trip/picnic etc.
The beauty of these newer Engels is that you can keep both 240v and 12v plugs in the back of the fridge all the time. As soon as the fridge detects the 240v it automatically switches to that power source in lieu of the 12v.
I've gone one step further and put a 240v cord up into the cargo bay through a large rubber grommet and run the cable along the chassis rail to the bullbar, where it terminates with a caravan style inlet plug. I have a 240v cable hanging from the roof of the carport and simply plug it in at the end of each day.
Also in the cargo area, I keep a small batt charger plugged into a power board kept on the cargo barrier. The 12 v outlet from the charger is plugged into a cigi socket also in the back. So when I'm running the fridge off 240v, I'm also charging the aux batt.
I don't like deep cycle batts because when on an extended trip and not able to use a charger, I have found that after a couple of weeks, the DC batt will progressively loose it's charge, even if being driven every day.
Just my opinion......it works well for me.
Cheers,
Roachie

Man... All you guys make hard work for yourselves....

I have a gelcell 145 a/h aux batt which runs - (compressor, invertor, fridge, hf radio, etc etc) and leave the fridge on 24/7/365 and never had a prob in almost 4years....

I can turn the fride to number 1 and it is still running after 5 days...