I have 2 fridges,a 60 litre ARB and a Bushman that is switched off, and lives in the back of my Hilux.
Both chill reasonably quick ,however,i have noticed more so with the bushman that if i pull up at the bottlo and turn it on,run inside grab a few coldies and pop em in the fridge,in the 10 or 15 minutes it takes me to get home the fridge will be down to minus 1 or so
I guess what im saying is ,empty,they will take a while to chill,but once something cold is placed inside it reaches its set point quicker