I’ve been using gas for years but just recently I started taking exact measures of fuel consumption.
My typical use is boiling 1 pint for dinner. That’s been taking 6-7 grams of gas. If I also boil 1 cup for breakfast, it’s around 10 grs. of gas gone per day so it seems consistent. Cooking for two (and thus doubling water quantities) gas consumption doubles too.
Most of the time I was using a stove of unknown brand (I got it on a trip and didn’t keep any packaging). Later I switched to a Coleman F1. The results are similar (just the Coleman is considerably lighter).
I just boil the water and switch the stove off. I’ve been using a windscreen/heat reflector that encloses the burner and pot bottom and if it was windy I sheltered the whole set somehow.
The conditions have been always very mild temperature wise but the water was usually cold from the mountain streams.
I always set the flame to low.
The target canister is not exhausted yet but I’d say I’d get around 20 days out of a canister if I boil water also for breakfast, around 30 if I only do dinner.
I must say the windscreen, cozy and use of a low flame have been relevant factors for increased efficiency. I wasn’t taking measures before but a rough estimate is it was taking twice the fuel it takes now for the task.