I did mean the coolers. OVM suggested a refrigerator. I don't think it's portable enough to work around in my c/v. I like your idea of taking it inside so it always stays cold. No waiting for it to cool down that way. I think the box also says that you need to put cool items inside, it won't cool down from a warm temp.
Yep, I often use a technique I used to use with regular coolers, that of freezing a bunch of small spring water bottles and using them to both pre-chill my 12v cooler and fill up empty space. As indicated in other threads, keeping it full keeps it cooler. Thermal mass. It will cool down from a warmer temp, though. I do it all the time. The pic with the lint/dirt shows the heat sink (I'm assuming that's what it's called) that the fan pulls air through from the cooler, which lets it escape. If putting anything on top of these guys you have to leave room for that air to circulate freely. Some drivers keep these units on their back as a chest cooler.
The one pic I att'd earlier shows where I keep mine, passenger seat gone. Here's the back view, from outside with the passenger door open; just one way to do it. Small easy to build shelf in front of the fridge holds my printer and organizer for everyday stuff on top, with room underneath for whatever, all below the bottom of window opening:
Lousy image, pretty dark, but hopefully you get the idea.
It is where I'll put my 12v/120 AC Truck Fridge too, which are built for the rigors of truck life. I had a dorm fridge in one of my old vans, but rarely powered it unless I had park power, so can't really speak as to how well they hold up. A lot of guys use them though, and as OVM said, they're pretty cheap at the big box stores.
Having your fridge/cooler there is handy as hell. When van camping I just turn it 90 degrees and have easy access to it from the side doors while standing outside.
Hope you figure something that works well for you!