Propane consumption by fridge depends on a number of variables

1)  Size and model of fridge - there are a lot of 'em

2)  Ambient temperature - the hotter outside, the more propane will be
burned.  If really cold, only pilot lite will burn - main burner will never
come on.

3)  What's inside.  We used to start our camping trips with  frozen "chubs"
of hamburger, breakfast sausage, and other frozen items to help the fridge
out.  It helped reduce consumption a lot.

4) If we precooled the fridge by running it on 120vac for 24 hrs or so
before our trip, less propane would be consumed.    

5)  If you expect the fridge to make ice cubes, etc. it will burn a lot more
propane.

Most of the places we went camping - mountain areas in WY and CO were cold
at night so we ran the propane-fired furnace.  Consumption by this beastie
was the limiting factor - not the fridge and the stove.  I expect if we had
only run the fridge we could have gone for 10 days - 2 weeks on one gas bottle.

good luck!

leonard jones