I've gotten 4 days and almost 5 from a small Snow Peak cannister in the Colorado Rockies at elevation with wind. Coolish at 45-70F, but not cold. I use a Coleman F1 Exponent stove that is a real fuel miser but do make two cups of tea in the morning as well as a full sized supper, sometimes with two different parts, at night. I find boiling just enough for a dried potato or rice meal and using a cozy really conserves. I measure the amount I boil for either myself and for a partner, then use the tablespoons of leftover hot water for dishes. A windscreen will extend the fuel cannister 20-30% on windy days and taking your cannister in the old sack helps with morning boils. Otherwise at close to freezing, I get frost on the cannister and it sputters.

We're tough here in the north, we use cold water on hands and face in the morning. Wakes you up. I have also found that 4oz of alcohol and my little alcohol stove is a good backup plan which will give you 4 boils in case you get carried away.