ChattyDM, in a recent post, talked about breaking the paradigm that campaigns need to be epic, multiple year long affairs, often going from 1st level to as high as you can get.
This has pretty much been the situation in any campaign I've DMed or played in. I wish I had thought of this sooner. Actually, now that I'm thinking of it, my campaigns usually were the short type, but only because I have Campaign Attention Defecit Syndrome. Especially in the early 90s when AD&D 2e was coming out with new campaign settings, I tended to bounce back and forth between them. From the late 80s to the mid 90s I ran the following campaigns:
D&D BECMI (Mystara)
AD&D 2e (Mystara, then Forgotten Realms, then Spelljammer, then Dark Sun)
At that point I stopped playing RPGs for the most part until 2003 when I moved back to Kamloops (except a couple of campaigns when I lived in Montreal for 18 months).
I probably would have ran a Birthright and Planescape campaign if I had been playing D&D at the time.
The bottom line is that I always tended to get excited about a campaign, then start it, but over the next year or so get bored and want to try the new shiny campaign.
I've been much better since 2003, with two long campaigns: a 3e campaign that I co-DMed from 1st to 14th and a 4e campaign from 1st to 16th.
However, even though 4e is the best edition of D&D for going from low to high level without breaking out of the sweet spot, the realities of life interfere with that. Our group on average meets only once every two weeks rather than weekly like we did in college. In addition, with combats taking fairly long at Paragon and Epic tiers, it would be on average two months before leveling up.
It's difficult to maintain my own interest, let alone my player's interest when campaigns might take 3-4 years to go from 1st to 30th level. That's only taking the story into account. If you consider that players want to experiment with other characters, given the multitude of options 4e has, it's completely unrealistic to expect the characters that start the campaign to be the ones that end it. Myself, I find that 18 months is the maximum that I can maintain my interest in a campaign.
In my last campaign, which was to end up with a big confrontation with Tiamat at the end, by the time we got to 15th level, only two of the six characters were even involved at the beginning. It made it difficult to really harken back to the very early part of the campaign without being a bit ridiculous.
My interest was starting to flag, and I had mentioned this to some of my players. One option was to advance the PCs to Epic level to finish the campaign off. In the end, I decided to wrap up the story as it was with a big epic battle (which I thought ended up very cool).
This is similar to the advice given today by James Wyatt in his Dungeoncraft article (DDI sub required).
If I'd been smart about it, I probably should have just hit the reset button right there. Although I'd had plans of running a campaign featuring Aboleths, Daelkyr and Cthulhu, I just couldn't get enthused about it (mostly because I enjoy the more grounded Heroic and Paragon tiers) and the campaign sagged for about two months before we decided to reset, go back to 3rd level and start a new campaign.
I'm going to be trying out some methods for speeding combat up using lessons I learned from Torg, and once I finished figuring it out, using a 4e D&D version of the Drama Deck. But most importantly, the campaign (War of the Burning Sky) has a definite ending point. Fortunately, the writers of the War of the Burning Sky saga have put in interim ending points if you don't want to do the full 1st to 30th level campaign.
At this point I think I'll be doing Adventures 1-8 and then leaving 9-12 for some other time. Oh and Dark Sun is coming soon too...we'll probably take a break in the War of the Burning Sky campaign to explore that.