Supply isn’t a measure of time or distance, it’s a measure of difficulty.
Sometimes gamemasters get bogged down in the details: how many miles could you travel in a day, or how many supplies would you exhaust in a week. This kind of bookkeeping isn’t bad; understanding how the world operates is critical to creating a place that feels real, but if the threshold for bookkeeping is too high, most players won’t engage (or will only engage if given a meta-currency, like inspiration or rerolls). Likewise, I’m still in the process of creating a system that unifies mechanics, and one of those golden calves for me is unifying the dungeon turn and the travel turn.
I have this idea that a sack of supply, to borrow a term, should feed into the dungeon exploration: a sack of supply to a point on the crawl should be something to the effect of ten turns of exploration in the dungeon itself. This idea (the use of sacks of supply) is shamelessly stolen from the UVG, but even in that great lofty tome, there was something about the tracking and usage of supplies in the wild that rubbed me the wrong way. I felt it as I ran the game for the first time: my players were getting into heated arguments about how many supplies they should have for how long they would be out for, but the tracking of the days and weeks and the changes in weather still frustrated me as I tried to run the game “rules as written”. I recognize that this runs counter to THE WISDOM. Not to mention UVG’s lack of delineation between an area (like Potsherd Crater) and a location (like the Porcelain Citadel). See for yourself.
In the Old Days™, a dungeon was only as big as its rooms, and the pride of each Dungeon Master was his Dungeon, a sprawling complex of hundreds of rooms and dozens of factions and treasures to satiate desires both subtle and gross. Hell, I think it was the person who writes the Hack & Slash blog that said that a person only has so many mega-dungeons inside them because it’s such a reflection of the internal emotional state of its creator (in this interview, I think?). However, for my games, I want the travel to the location to be part of the journey, not just a handwave to the “fun part”. Likewise, I’d like the quantum style of supplies to be applied to the dungeoneering kit that gets broken out once you do reach the location. You get a sack of supplies to the dungeon, you get to specify exactly what’s in the sack, as needed. (This is also a choice: leaving it in its quantum state means it’s still food to eat, actually looking in the bag means you now have a tool to use specifically.) I also want my players a little more focused on the travel to the place than completely focused on the destination.
The most you could squeeze out of one supply sack is probably about seven days of easy traveling in beautiful country. You could travel about 48 miles on that single supply sack, and the only encounter you might expect is miles away, easily avoidable. The travel time would be spent just laying in the back of the company wagon, or sleeping, or reading, or working on your own book, or riding ahead of the caravan to pick produce from the blossoming fruit trees or watching the herds of wild horses in the distance.
The harshest use of supply sacks would be something like five sacks of supply per person for something like a single day or two of travel: faced with a deep gorge a half-mile wide and a hundred miles long, with the only way of getting across being climbing and hauling your wagon with rope down to the bottom, carefully floating across a wide river full of rapids, and then waiting for the rogue to climb up the other side, hammering pitons into place for the ropes and having the barbarian pull the rest of the supplies up to the other side. Everyone is tired and spent. The sack of supply represents it all (in the quantum state): the extra rope, the hammer, the pitons, the tar in the seams so you can caulk your wagon. However, it’s not the single day that’s the worry, the time and the distance is the flavor. The sack is the important part and the ability to carry sacks (especially big sacks of treasure) is why it matters.
Or maybe five sacks to cross a particularly flat steppe with no real difficulty in controlling the wagon: the extra sacks of supply are to bribe your way through fantasy Comancheria with your scalps on your heads and your balls not sown into your mouth. This example is interesting because it points to the other aspect I like: the sacks of supplies are negotiable. You can’t argue that a place can be closer, or that time won’t flow while you travel there, but you can argue that it wouldn’t take as many supplies to get there. Maybe you roll well on a Charisma check and can convince the Comanche/Mongols/Cossacks that you don’t have to pay as much. Or maybe a skilled scout might knock a two supply trek down to one with a good Wisdom check. Or maybe you already have the rope, not part of a supply sack, something you bought specifically, that you would use in place of the quantum use supply sacks needed to get to the bottom of that gorge.
These are all just ideas at the moment, and the big hurdle is tying them into wounds and the ability check.