"Green Armadillo, given the corporate need MMOs have to simultaneously nullify the accomplishments of the previous expansion when introducing a new one, but also give benefits to lapsed players to catch them up quickly, wonders if it just makes sense to skip every other expansion to get both the benefits of a hand up and a debugged game?"
Though I'm humbled, as always, to see the essence of what I spend pages on distilled into a single sentence, I have a few more comments (pages) on the topic.
Time is money, but how much?
There are two costs to playing an MMORPG; time and money. In the comments to my last post, DeftyJames rightly pointed out that I focused too heavily on the cash cost.
The cost in cash is very easy to quantify. A player who bought LOTRO's Moria expansion and payed for a three month subscription at its launch in November paid $85, while a player who waited until the current promotional deals a mere six months later would pay only $40 for that same expansion key and three month subscription. It's very easy to conclude that the player who waited until May saved $45, a moderately-sized sum that could pay for three months' subscription fees to the game of their choice.
During the six months since the launch, Turbine has also been fixing bugs and adding additional content. As a result, the player who waited until May is ALSO getting a superior gaming experience during the three months they're spending on playing the game. There isn't an easy way to quantify how much better that experience is, but fewer bugs, more polish, and more things to do add up to a good deal all around. The catch is that it doesn't matter how much better the game gets if you never play it because you're always waiting for it to improve.
In search of the sweet spot
Now we're looking at a meta-game incentive; neither the cash cost nor the quality of the gaming experience are actually in the game. How do we find the sweet spot, where you'll get the best value for your gaming time and money? The answer depends on what you're hoping to do.
If you want to do a lot of pick up groups, perhaps it's best to tackle content as it comes out when there is the most interest. Or, as Ayr suggests, perhaps it's best to arrive later in the game when players have learned how to beat the content. If it's harder to fit group content into your schedule, and you're more worried about having flexible solo content to tide you over, perhaps it makes sense to wait for subsequent patches. Then again, sometimes subsequent patches will trivialize content that didn't need to be changed.
Ultimately, this is where my compromise suggestion that the best time to play LOTRO Moria may be right after the launch of LOTRO Rohan came from. If you move at a moderate pace, you can experience Moria in its final form and still arrive in Rohan while interest is high and content has yet to be nerfed. It's not perfect, but it gets you some of the best of both worlds.
Usually, I write about out-of-game meta-analysis of an in-game incentive of some sort. In-game incentive balance is easier to fix; if players aren't doing the content in the correct numbers, the developers should change the incentive. When the incentive - future patches that improve the gaming experience - is not in the game itself, the water gets murky.
From a business side, studios have major incentives to focus on major releases. You won't get retailers to give you prominent shelf space for an incremental patch that adds a new zone, but you CAN get launch hype for an expansion that adds half a dozen. A monthly patch with a few features won't get much attention from the press, and may not contain anything of interest to people who do hear about it. A megapatch, arriving every six months with something of interest to every single player who hears about it, will make some news, which is part of why Blizzard has gone that route with it's post-TBC patch cycle.
The problem is that this schedule, while convenient for production purposes, creates the out of game incentive NOT to play the game all the time. If you're Blizzard, you don't need to worry about this because you have so many subscribers that it doesn't matter of some of them cancel for half of the expansion cycle. (Given WoW's notoriously slow expansion cycle, my best guess for its "sweet spots" would be right after the expansion launch and right after the last content patch of the expansion, skipping the middle two or so content patches, and possibly some of the dead time between the final patch and the next expansion.) If you're running a game with a smaller subscriber base, though, that kind of disruption to your revenue could be fatal.