How to Keep Players Returning for a Thousand Hours

As noted elsewhere, I've run a lot of long campaigns. (I don't currently have an ongoing game that has lasted less than three years. My longest campaigns lasted eleven and eight years, respectively; one of my current ongoing games has continued for six-and-a-half years.)

Bearing that in mind, one of the most common complaints I see on the internet is about Game Masters attempting to wrangle players and force them to enjoy the GM's nonsense. To answer those complaints, here's a short list of advice, in many ways a coda and distillation of the advice I gave at the bottom of this post. Enjoy!

1. Don't cancel. If the players have to cancel, that's one thing. But in my experience, if the GM habitually cancels, everyone assumes the game isn't a priority and their attention wanes. Stay home if you're sick or there's an emergency, but otherwise, do your best to make the game a priority and your players will do the same.
• If you have to cancel, give as much notice if you can. Otherwise, even if you're feeling unprepared, this might be a great opportunity for a breather session.
• If you can establish a regular schedule, that's even better. Don't break it unless you absolutely must.
2. Listen to the players and make their choices matter. Table-top role-playing games have two big selling features: players can try anything they want (as long as they're willing to live with the consequences), and it's the only activity in this cyberpunk hellscape where a participant is guaranteed an actual living human's individual attention (as a reward rather than a punishment). So give it to them: let them try whatever they want and live with the consequences as long as you telegraph the consequences in advance.
• You don't have to tell them exactly what will happen, but "if you fail this jump you'll fall" and "you don't know what will happen if you mix those potions together" are good starts.
• Also, let consequences echo throughout the campaign. Players love it when a dangling plot thread from a year ago makes its triumphant return.
• You can do this even if the characters aren't "important." The cashier at the corner store notices that you haven't been around in a couple of weeks; that establishes the character's place in the world and suggests that someone cares about what they're doing.
3. Establish real stakes. A series of 300 scripted fights might be fun as a tabletop combat sport, but it makes for a boring longform campaign. Dig into why the characters are doing what they do, and play antagonists as intelligent characters in their own right. Everybody wants something, and has stuff they're willing to do to get it. What does that mean for the NPCs? What does that mean for the PCs? Even if the players are no-backstory dungeoneering chumps engaging in 1974-style fantasy adventuring to get gold to gain XP to build a domain, that's a plot detail that should probably come up before Level 9, right?
• On a smaller scale, not every encounter with hostile forces should lead to combat, and those that do should feature creative use of equipment, terrain, traps, tactics, and even more ephemeral things like positioning and time limits. A fight even against weaker opponents is more interesting if they have hostages, while C1: The Hidden Shrine of Tamoachan increases the difficulty by giving the players a time limit while delving the dungeon.
• Even if events become world-shaking, always bring the game back to the player characters' scale. They're not saving the world, They're saving the people in it. They probably even know and like some of them!

That's basically it. You should show your players all the courtesy you want a friend to show you, and they'll keep coming back to find out what happens next.