Joe Bob it really depends on the size of the fridge. Have a look at the fine print on the fridge or alternately "Google" for the fridge specifications. You should be able to find its consumption expressed as grams per hour or similar. Then it's just a matter of doing the maths to calculate how many hours from any given bottle.
To those who leave gas fridges running at petrol stations, I suggest you search You Tube for gas station fires. It mightn't have happened to you .... yet ..... but it does happen!