Out of curiosity, do you create a new world for every campaign? Or do you re-use worlds?
I guess a new world for every campaign. But I've only did one fully home-brewed world in the 10 years I've run games since getting back into the hobby with 5e. After a year or several years of running a campaign, I'm usually looking to do something very different for the next.
My first campaign was entirely homebrew. I did work in some published material into it, but only where they made sense for the setting and what the party was up to. The world map, cultures, cities, etc. were all home-brewed. I ran that campaign from March 2015 (I had working on the campaign world in the winter of 2014, before I started running it) until December 2017. I was exhausted with the prep time I was putting into it so my next campaign was Curse of Strahd. Ran that from January 2018 through October 2018.
I then started a Rappan Athuk campaign in October 2018 and we finished that campaign in December 2023. For that campaign, I tweaked, borrowed, and homebrewed rules for factions, reputation, downtime, and strongholds, but initially ran the adventure and setting material as written. But over the years, based on the PCs actions, I changed things.
Now I'm running Warhammer Fantasy 4e, mixing the various published Ubersreik material with the Enemy Within campaign. We started that in January this year.
I would like to go back to running another campaign in my homebrew world, advancing the timeline by several centuries. But my work and family obligations don't afford me the time do put the work in.
To scratch my "world building" itch, I instead occasionally run one shots or mini-campaigns with rules-light systems, like InSPECTREs, Dread, Grim, and Dialect. The adventures are more improve and collaboratively created, but I get to present the setting. It very much mini-setting building, but it is fun and allows me to play with a bunch of ideas and seeing what the players create from it.
I'll admit to being a bit precious with my homebrew D&D setting and have gotten very negative reactions in threads when discussed things like character limitations. It is very much an example of enjoying the secondary hobby of creating and curating a setting for players to experience. I know it isn't something everyone would enjoy, but my players enjoyed it.