One thing I mentioned in my glad-I-did/wish-I-did list was hiatus rules for characters. Meaning reprieve from upkeep.
Summary: I allow characters who haven't taken any game action whatsoever for one game month to accumulate no further upkeep, disease checks, or parasite checks. Any loans, domain costs, and hireling/henchmen costs still accumulate.
I have seen first hand that playing with character stables from session zero is a winning strategy. Unsurprising, since I stole session-zero stables from Anthony Huso. If you're unfamiliar with the concept, the basic idea is each player has a few characters in their "stable" that they can choose from for a given expedition. This opens a ton of strategic doors, provides for a variety of gameplay, and lessens the impact of a character death. When new players join our campaign they get three slots. After a couple real-life months this increases to five.
Stables have paid huge dividends in our campaign, and they can pay them in yours too, whether you run a huge open table or a two-person game.
Anyway, the thing to keep in mind is that once a character is played once ("activated"), they are on the hook for upkeep. At low levels, this means 100 gp per level per game month (we use the highest level for dual/multi-class), plus disease checks, parasite checks, and loan payments.
With 0 HP bedrest, training, and travel, characters are going to be unavailable for adventuring for strings of game days right from the start of the campaign. This means that wise players will activate additional characters from their stable so as to not need to wait around for the busy characters to adventure again. Time is perhaps the most valuable resource in AD&D.
Activating other characters is good. But sometimes many are activated to fill in for a particularly large deficit of adventure-ready characters. Or one player might end up with a disproportionate number of activated characters because a certain class is needed and only one player has that class. At an open table, you can also run into situations where some players are more forthcoming with activating new characters than other players.
After the campaign had been running for a few months, I realized that being on the hook for 3+ characters' upkeep might be causing some players stress that is counterintuitive to the goal of character stables. As a DM, I want to encourage the use of multiple characters, not add burdens.
To this end, I simply created a rule that says as long as a character has not taken any action for one full game month, they no longer accumulate some forms of upkeep. "Action" includes anything, including communicating with other characters, traveling, or gathering information.
The upkeep I limit to one month's worth in this case includes:
Upkeep that never pauses includes:
I categorized upkeep this way mostly because the first group is out of a player's control. Furthermore, I can imagine an adventurer on hiatus having negligible costs and receiving cures from a local temple as a regular person might, since they are not acting as an adventuring character at that time.
Is it a stretch? Too generous? Perhaps. Though I think the benefits outweigh the cost, and make for a better game.