Clever design, that....I know that as far back as D&D 3.0 there was a design notion that the average group played for 1 year, maybe 2, and that the leveling/XP should pace for campaigns that lasted this long, but the reality proved to be less stable than the spherical cow teams that WotC used to design the game at that time, with most groups getting exhausted by the complexities of high level mechanics around level 10-12. Even today, D&D 5th edition, which I feel has an advantage of easier play at high level while suffering from a dearth of high level content for the GM still requires a bit of an XP slog to advance....less than prior editions, yet more onerous than contemporary gamers care for. Or any gamers, really.
Pathfinder 2nd Edition, by flattening the progression to just 1,000 XP/level, has created a reward mechanic which lets the GM easily pace the game at a consistent speed with regards to leveling, which is cool. I've experimented a bit, and found that 2-3 sessions per level is quite comfortable, but a stoic and determined GM could pace it out to four or more sessions using the RAW and could even for a gonzo "13th Age" approach and do a "20 sessions, 20 levels" kind of campaign if they wanted to. PF2E can handle it.
In terms of game campaigns I have done the following:
Oman'Hakat and the Lands of Osinre and Harkuum: I have spent most of my effort in a campaign setting of new design which I call "Oman'Hakat," the Final Realm. It's a strange bedfellow to my most venerable setting, Ages of Lingusia, and one of the overarching plots is how the two worlds connect (and why). The setting is aimed at a land of archaic kingdoms and a budding empire, with a period of deep religious upheaval and fear of prophecies spelling doom for the world. A major part of the mystery is dispelling the fiction from the truth of the game's own history and folklore.
I started this campaign in D&D 5E in the months leading up to Pathfinder 2E's release, setting the 5E games in the Osinre region of the world (based on Egyptian thematics), with the joke being that the distant, ominous empire of Harkuum would be to staging ground for Pathfinder 2E games. So far this is exactly what has happened, though when we do finally revisit Osinre it will also be in Pathfinder 2E. Either way....with any luck I'll start posting some of the massive amount of content on this setting I've worked out on the blog soon for general and free consumption.
Ages of Lingusia: I have revisited the Age of Strife era in my oldest campaign once more in one of the every-other-week campaigns, focusing on a gritty, dirty corner of the world about ex-soldiers seeking to recover from the traumas of a war which the were on the winning side of, but at great cost. It's proving to be very fun, and I love that Pathfinder 2E's more visceral approach to fantasy with a clearer level of risk and grit makes for an excellent fit in the world I originally created for AD&D 1E.
A Brief Return to Enzada: My exotic campaign I devised specifically for use with Pathfinder when it came out, designed to invoke all sorts of anti-tropes for fantasy, played out in a quiet revisitation over a few months before I decided I just wasn't feeling the impetus to see where things went and we migrated to Lingusia. Still, it's nice to explore old setting now and again.
Chirak: I haven't yet done anything with Realms of Chirak for Pathfinder 2nd, though the temptation grows by the day. I am biding my time, waiting for that moment of inspiration to spark; I ran a lot of games in Chirak over the last decade, and the venerable setting has earned a break. I am tempted to keep it with D&D 5E, too; I put a lot of work into upgrading it to that edition, after all. But D&D 5E just doesn't feel right now that I've been playing Pathfinder 2E so much.....still, I may go back and revisit, see how I feel about it with some actual play at some point. But no rush; Chirak's many lands still need a break.
Anyway, with one group going from level 1 to 11, another group creeping along from 11 o 13, and a third starting at 5th and migrating up from there (plus one campaign that ran from 1st to 5th now retired), we're already gotten in a ton of Pathfinder gaming with no end in sight. I am really looking forward to the release of the Gamemastery Guide 2nd edition next week, a much needed tome for GMs which I am keen to explore. I'll provide more info once I have my copy next week!