Lots of downtime.
We are playing a Rappan Athuk campaign with Matt Coleville's Strongholds & Followers rules. Building up and maintaining their strongholds and the various political and business opportunities and challenges that this creates is a big part of the campaign. Beyond providing something to spend money on and to need lots of money to maintain, it is also the base of power for the parties continued pushing back of the forces of Orcus.
Previously, we played one 8-hour game each month and the then played downtime in between by e-mail. Now that I'm overseas, we'll play maybe twice a month and will probably take care of much of the downtime in game. Or at least, now that they have access to teleport circles we are beyond the bookkeeping of travel and lifestyle expenses. The gains or losses from their stronghold and businesses are larger and quicker to resolve. There is less benefit to spending time on gambling, carousing, working, etc. Now, other than training, the only individual downtime might be buying or selling high value items or acquiring information (carousing, researching).
Downtime keeps the setting alive and is building new party-centered plot lines from organically derived goals. What makes downtime work well with our group will not be everyone's cup of tea, but it includes:
1. GP = XP.
You gain XP by extracting treasure and from some milestones. There is no XP for killing things. This results in a more creative, problem-solving style of play, where you might go up against creatures stronger than you, by sneaking, not fighting. There is no benefit to killing large mobs of low-level creatures, so the party may ally with them, demand tribute, or just leave them be.
2. You have to train to level up and training costs gold.
This was a significant driver to get gold at low levels. At higher levels it is not so much a challenge as just another way gold is spent.
3. Xanathar's Downtime Rules
The downtime rules in XGE (along with a mix of PHB and DMG downtime suggestions) were used heavily at lower levels. But after they acquired a stronghold, I stopped bothering with lifestyle expenses. Also many of the downtime activities in Xanathars become less valuable as you level up. About the only ones still used heavily are info-gathering activities. Carousing and research are still heavily used. Nobody bothers with gambling, working, or most other downtime activity now. Buying and selling items can be handled by followers, so only very special items involve an individual PC's downtime.
4. Factions
I modified the faction rules with the reputation rules published on EN World a while back. I further added some rules to allow buying reputation with GP (e.g. donations, bribes, contributions, depending on the nature of the faction).
5. Strongholds and Followers
I've pretty much incorporated this book's rules as written. They are working very well in this campaign. It gave a goal to save gold for and the party is still working on getting more gold to level up their stronghold.
6. Round up in the book keeping
As the party levels up, expenses that were once significant become far less so and tracking them become tedious. I figure they have "people" to manage that and I just abstract the expenses to make it easier. BUT I ROUND UP! Expenses are never rounded in the party's favor. Strongholds give some very nice benefits in Coleville's book, but the party still needs to feel the bite in their pocketbooks.
7. Slow Leveling
We've played about 70 hours (at-table play, not between-session downtime) and the characters are at about 5th level. One player is at 10th because of some weird Rappan Atthuk swingy magic encounters that can go very bad or very good, which I won't go into because of spoilers.
At 5th they are already property holders and political players in this backwoods wilderness area that is on an important trade route.
Almost three years have passed in-game.
It is very different from most 5e play, but I like spending more time at lower levels, and really developing the characters and the party. Its not save the world, grow for barely competent to legendary in weeks or months. It is more of a long victorian-era novel.