The adventures varied greatly, with the players visiting almost every Outer Plane or its corresponding Gate Town. It was a great voyage that tended to veer towards the silly or over the top, though with some amazingly powerful emotional turns surrounding the owner or Planeatary Express Balial and the mad scientist/murderer Valran. I consider it one of my more successful campaigns.
The last Planescape session. Notice the Acheron poster!
It is always strange to end a campaign. A lot of emotions and desires build up, and as a GM you're trying to deliver the perfect closing experience. It just comes up so rarely because most campaigns tend to die by about the third session.
I've been lucky and been able to successfully begin and end multiple campaign. A simple strategy I've used to get experience accomplishing a complete campaign is designing campaigns with limited life spans. For example, I would only run 10 week campaigns. This was exactly the length of a quarter at my undergrad university.
Because I tend to design episodic campaigns, I initially struggled with figuring out a satisfactory way of providing a satisfactory ending. What tends to end up happening is that I create a negotiation scenario with the PCs. Try and figure out something that bothered them about the world or their previous adventures that they wouldn't mind going deeper in to. Most of the time I can intuit what this is, but some times I have to ask the players to go along with me in order to actually end the campaign. The latter of these has really only happened when the campaigns had to end because I was moving countries.
Do you, reader, have any ideas about how to best end a campaign?