I’ve played in two separate styles of “rotating”/multi-GM campaigns, and honestly had good, albeit very different, experiences in each.
In Game A, a group of longstanding IRL friends and I got together after we’d wrapped up a Pathfinder campaign and wanted to do something very different and much more story-forward. I suggested a Fate game, with a novel setting built together using Dawn of Worlds. We spent a good three weeks really digging deep on the DoW stuff, with each player portraying a sort of divine force sculpting the world’s geography, then inhabiting species, and then socio-political history. It was all also gloriously weird and very gonzo and silly, in keeping with our sensibilities. Folks were worried it’d be hard to turn that giant twisty-turny map of nonsense into a proper campaign, though mercifully, a handful of conflicts/dangers had emerged through the DoW play.
GM 1 started us off with a questgiver NPC sending us off to collect a Thingamajig for a Dark Purpose, and off we went, playing about 8 sessions under his guidance until the Thingamajig was acquired. Then, as some others in the thread have discussed, one of the PCs went off on a personal questline (specifically, mine, since I was to be GM #2) and another hook was dropped for another 8-10 session arc. Just ahead of GM #1’s last session, we did briefly talk about how to transition my PC out (the nefarious Questgiver NPC had managed to acquire my PC’s long-lost sister from his backstory, and if my PC agreed to work for QGNPC, he’d free her at the end of a term of service). Subsequent transitions were handled similarly: one GM’s PC was zapped back in time during the climactic moments of The Big Fight at the end of an arc; another sold his soul to a demon to return the time-zapped PC to our time and had to go away himself for awhile; while yet another wound up going on a quest to reclaim her god’s favor and find the demon-serving PC (coincidentally before he managed to escape and catch back up with us, but not in time to stop her leaving, of course!).
Since we were all familiar with the world and some of the major conflicts in it, it was relatively easy for us to each generate an interesting short arc to push people through – we even developed a series of spur-of-the-moment one-shots when a player would call out of a game night late and we wanted to wait on them before resuming the main storyline. Of course, given that most of us were also longtime GMs, I like to think we had a pretty decent sense for story and development, so we also generally tried to hook our new arcs onto the unresolved plot-threads from prior ones.
Over the course of about 4 GM swaps (total of 5 GMs/arcs) and a year and a half of play, we managed to tell a pretty cohesive ongoing story that slowly focused in on one of the “ticking time bomb” potential apocalypses we’d scattereda round the world during the DoW play. Despite being very silly and more than a little NC-17 at times, it was a genuinely great campaign with a surprisingly solid throughline, despite very different GMing styles.
Not much planning went into it, apart from a quick chat about how to handle character-departures during swaps, though we did end up with a decent-sized little packet of NPCs and locales we’d share between GMs at each swap that had slowly built up – maybe like 5 or 6 pages total?
Example 2 is simultaneously more complex and thus somehow even longer to describe (sorry, I can be very wordy 
) , and specifically focuses on multi-GM play, though technically, GM swapping also occurs. See more below!
I’ve spent a lot of the last few years wrapped up running for and playing in annual, seasonal, serialized campaigns hosted by my (amazing!) local RPG group, Raleigh Tabletop RPGs, that we call SOPs (Semi-Organized Plays). Each SOP runs for 3 months, with game sessions run on 2nd/4th weeks (Fridays or Sundays, depending on the campaign) for a total of 6 sessions any participating player can join in on, plus – usually – a Session 0. The format is somewhat novel in that teams of 4-6 collaborating GMs work together to run multiple independent sessions each game-week that are understood to more or less be happening simultaneously. Not all GMs run each week, so 2-4 tables worth of novel storyline content is revealed each week, building toward some kind more-or-less planned climax in each season – some of the campaigns are more player-driven than others.
Each quarter (Jan-Mar, Apr-Jun, Jul-Sep, Oct-Dec), a new season of SOPs starts, and the prior campaigns wrap up for the year (with successful ones returning in the same slot in subsequent years, until retirement, whereupon new teams of GMs can add a new SOP to the schedule). Over the years, we’ve put on 10 different SOPs; a few only made it a year, while The Contingent (urban fantasy/horror using Chronicles of Darkness to tell the story of a privately funded New York-based monster hunting organization) and The Miskatonic Society (historical Lovecraftian horror using various versions of Call of Cthulhu to tell stories in different eras ~1880s-1940s) are both on Year SEVEN in 2021!
Truth be told, I adore our SOPs – enough that I’ve helped run some seasons for two of them and wound up founding one myself – Seek the Stars!, a scifi action-comedy space opera now using the updated Fate Condensed system to tell the tales of “Expeditionary Team Alpha,” a down-on-its-luck special ops division of definitely-not-Starfleet – that’s in the middle of its fourth season right now. Much like the Gauntlet Calendar’s plethora of 3-5-session mini-campaigns, you can tell a really tight, satisfying story in that span, and the multi-table structure lets a lot of players experience fun, engaging personal arcs along the way.
That said, there are absolutely limitations and issues. SOP seasons are by their very nature limited, since as one block ends, we immediately move into the next – there’s no room to push past the 6-session max, so you’ve gotta really tell a tight story. To help keep later session prep relevant (the GM teams often prep for months in advance on these suckers!), stories tend to be a little more on-rails than any of us would ideally like, though the players are absolute champs about rolling with that and engaging with the settings. And, well, when you’re juggling a rotating cast of 10-20+ PCs each season (who can move freely between tables each week, shaking up group compositions and potentially letting them follow different plot-threads each time around!), it’s tough to really dig deeply into any one character. I think it’s closer to a home game than, say, Pathfinder Society, but there are some major differences, of course.
And, as noted before, the prep can get a little crazy. We’ve got incredibly elaborate player-facing Wikis to store PC info, NPC listings, story histories, player-written journals, and lore dumps. And behind all that, most of the GM teams maintain even more elaborate internal data stores to house their session notes, NPC backstories/motivations, season planners, custom rules docs, etc. Most of the teams use Google Drive for this, and work for 6-9 months on each season. Mind, said seasons often entail 3 Session 0 tables, and then 3-4 inter-related-but-independent “one shots” in each of the 6 main sessions – some seasons have featured a total of almost 30 games run!
And writing satisfying sessions for this format is incredibly challenging: you simultaneously want to contribute to the ongoing season-long arc, respect player activities and prior season plotlines, leverage existing NPCs and locations but also introduce novel elements to the players, engage with backstories and sidequests for a group of PCs you only learn about a week in advance (when players signup and fill out surveys to indicate which session they want to play), and still tell a tight, individually satisfying, 4-hour story that must conclude and convey all relevant arc-info in that time span, because the schedule’s definitely too tight for you to squeeze in a makeup game.
Hah, needless to say, burnout can get pretty bad for GM teams, so we proactively limit people to only GMing in two of these a year, only show-running one of those at most, and never running all 6 sessions of any given season (ideally 4 at most). But the results are fantastic, and having played in a ton of these by now, I can absolutely say the player experience is really amazing.
It’s a lot of trouble, but very worth it, in essence 
