I might not be interested in playing out downtime in detail, but I do like it when there are downtime systems that let me work on long-term stuff without taking up a whole lot of actual game time, perhaps with the chance for some hiccup that requires involvement. The Troubleshooters is nice in this regard. Depending on how much time passes until the next adventure, you get 1 to 4 units of downtime to spend (this is not linear: 1 for a week, 2 for a month, 3 for half a year, and 4 for a year or more). These units can be spent on:
- Crafting: make one of the (usually) five skill checks needed to build a non-standard item.
- Mend & Recuperate: get rid of the Wounded condition if you ended the last adventure with it.
- Shop: Get an additional gear kit of mundane gear. You can still only have so many gear kits available to you at any one time, but this provides more options.
- Socialize: Meet an interesting NPC and get to know them. Write about half a page of stuff about the NPC, which the GM can then use in future adventures. You start the next adventure with an additional 2 story points (so 6 instead of 4) for helping the GM make the world more interesting.
- Train: Get an additional improvement check on a skill, or a tick toward learning a new Ability or language.
- Travel: As Socialize, but for a location instead.
Usually, you can only do each of these things once in any downtime period.
Even that's more mechanical than I'd like. Common downtime activities I see are:
--- training to level up
--- treasury evaluation, identification, and division
--- work on non-adventuring projects e.g. building a home or ship, getting involved in local/regional/national politics, etc.
--- interaction with NPCs not connected to any adventure e.g. a PC's friends and family
--- information gathering, includes spell research, mission research, and so forth
--- shopping and restocking, also selling of excess or unwanted items and gear
--- carousing, partying, etc.
--- recruiting new adventurers to join the party, if needed; along with other party-member turnover e.g. retirements, etc.
--- pranks and practical jokes
All of these can and sometimes do happen during a single downtime break; and IME the session time spent on downtime breaks is almost always determined by a) the complexity of the treasury that needs dividing and-or b) the level of difficulty encoutered when gathering information. I usually guess it'll take a full session for treasury-training-etc., sometimes it's faster, sometimes it ends up as 2 or even 3 sessions.