What factors, in terms of in-game or outside the game itself, are the requisites for a Long-Term RPG game being successful? Can we define a list of things you MUST have for the campaign to work?

Good players committed to a lengthy campaign.

And it is a commitment. A casual crew who miss sessions, bounce in and out, etc aren't good for long campaigns.

A long campaign needs players who say "yes, I will show up X sessions per month for the next year or two and play this one game every time."

Location, location, location!  A setting that everyone likes, wants to develop and use.  One that makes whatever system being used less of a concern.

I don't know that there is a one-size fits all, but these two stand out for me:

I think an important thing is that the GM know how to adapt to developments that could shorten the length of the campaign. Those could be plot elements but also they could be on the player end (i.e. changes in the player line-up, changes in player interests and attitudes, etc). Being able to react to that is important.

Organization is also really easy to overlook, but a very basic step in keeping things going for a long haul campaign. If you don't know which NPCs are dead or alive, for example, that can be a big problem. So tracking your NPCs, events and political changes in the setting, etc.

A DM that can keep track and keep the energy going week after week.  And as I said in the other thread engagewith what the players bring.

I can be the commited player.  I run out of steam after about a month of DMing.  Its a great month but after that the energy of planning the event, plotting the adventure, and playing the damn thing, wear me out, I'm still having fun, but its just not as good.  Some times I forget things.  Sometimes I don't wrangle my players in time and we never get together.  

I work with in my limitations and I am trying to expand them. But a DM with the focus and commitment is essicential.  

After that 1 committed player (more is obviously better.)

Then compatible scheadules.

Then a place to play.

Simple physical stuff.

My generic high-level answer is it's whether there are players who are eager to play that campaign with that GM, enough that they choose to keep showing up for it despite the other things (whether other games or non-game stuff) they could spend their time/energy on.

I'm opposite SpinachCat.  I need players that are willing to deal with the reality shifts and compromises that results when people inevitably miss.  My schedule will never allow for a set thing.

For all my practical purposes, a system that allows some mechanical character growth is a must.  I can see how with the right set of players, that's not necessary, but I think I'm too set in my ways now to change on that front.  When I play a game with characters that stay much the same, I generally want it to be short.  (Though it need not be a lot of growth, just some.  A high level Fantasy Hero game where a point gained here or there hardly made a difference is still fine.)  More generally, I would state that as:  "Use a system that supports mechanical growth OR have players that don't care about mechanical growth."

The players need to get along, and not just in the "we are here to game for two hours, set aside out differences" mode, either.  It needs to be either genuine group chemistry or a firm, enforced desire to keep it all focused on the game instead of personalities.

The GM needs mental stamina.  There are a 100 ways for the GM to give out, and all of them have to be either managed or not relevant to this group.

Commitment on the part of all involved is absolutely essential, yes.

Players.

Everything else is just a plus. You can have everything else but without committed players the campaing will not go very far.

People
Snacks
Setting
System

(and Time - a regular schedule is essential)

Off the top of my head,

In Game:
Motivation for the characters
Consequences for their actions
A fear of actual loss or death
A sense of mystery
Balance of in-character dialog with action

Outside the game:
Players allowing their characters to suffer adversity
Abandonment of electronic devices whilst playing
Dedicated attendence
Trusting the GM

Quote from: RPGPundit;1006712What factors, in terms of in-game or outside the game itself, are the requisites for a Long-Term RPG game being successful? Can we define a list of things you MUST have for the campaign to work?

• Players and GM enjoy the game
• GM who is flexible with plots, events and scenarios
• Players who buy into keeping the campaign going
• Several distinct/interconnecting plot lines
• NPCs who regularly interact with PCs
• PC Goals being part of the campaign
• PC/Campaign Goals that can be reached
• Actions have consequences

Quote from: RPGPundit;1006712What factors, in terms of in-game or outside the game itself, are the requisites for a Long-Term RPG game being successful? Can we define a list of things you MUST have for the campaign to work?

 Motivated players + a system and campaign world I dont get bored by after 3 sessions. Generally some IP that I can fully be fully immersed in through other media like litterature, comics, video games etc to keep my interest and motivation going.

Referee
Player group (playing with whoever comes is possible)
Setting that is actually fun and engaging
A system that doesn't suck when used over and over
Dice
Snacks
Beverages.

Beyond committed players, I think the GM needs to have a broad vision of what he wants his campaign to be.