There is no standard answer to this question as everyone uses gas differently. Of course, it also depends on the season you are travelling in. In summer, it is unlikely that you will be using gas for heating, so a gas bottle will last a lot longer if only being used for the fridge and showers. Often you can get around 14 days from one bottle. During winter, when heating is used often and hot water showers are favoured, a gas bottle may only last two to four days.