This is exactly the opposite of the kind of system I am talking about.I really like the resource die mechanic in Forbidden Lands. Instead of tracking how many things you have the die marks your supply. A D10 roll of 1-2 at check time reduces it to a D8 and so fourth until you are out. Player is informed on the supply and they get to decide when its time to re-up. I knwo this is more abstract than a strict weight and consumption model, but it also allows for a lot of factors. Maybe the PC rations their food and water well. Maybe they get lucky and the supply last longer than expected. However, they could also lose supply, it could go bad, etc.. Adds in a luck factor and makes it simplified for simulation purposes without bogging down play in minutia. YMMV.