arcady said:
Consider a game going for months, deep into a very complex plot that the player have chosen and taken an active role in. You show up for session 37, and the PCs suddenly decide to walk away.
If you have a whole pack of NPCs and events that are planned to go off, and they still happen after the PCs walk away, or some of those NPCs come after the PCs... have you taken away the free will of the players to control where the game goes?
My gaming group, playing in my Forgotten Realms game currently, have finally come up with an appropriate name for their "adventuring company":
The company of the Endless Bridge. They can't finish a quest for the life of them.
Travel to Sembia to make money? Just as they get there they hear the news that Tilverton has vanished, decide to head West to Cormyr and render aid. They get to Tilverton, see a smoking grey dimensional rift, decide it's not for them, and head to Myth Drannor. They get as far as Shadowdale, decide they are too inexperienced, and head to the Moonsea, and the Zhentil Keep / Phlan region, to make their fortunes.
The gods only know what'll happen when they get there - if they don't decide to turn around and traverse Anauroch or The Great Glacier instead.
But simply put, events go on without them. I make sure they know it. In one plot, they could have rescued and befriended a Silver Dragon and its young; instead, they left the area, and I had a rival adventure band succeed. Soon, they will meet up with the rival band (which they know) that had gained the favor of a Silver Dragon.
They failed to uncover an assassin's reason for stalking a party member. The assassins will show up later, with a vengance, getting stronger each time until they succeed or are stopped.
Cormyr needs heroes right now, and all the name players (Khelben, Vangerdahast, Elminster, the Simbul) are out of commission. This will have repercussions later.
Keep the world moving, and no matter what the players choose, they will see that if they don't stick to a plan to its completion, they will suffer consequences later. It's not punishment, it's a lesson in cause and effect.