I have to wonder with the people who are complaining that it is too soon, what tim they all started playing GW. I started when it first came out and I have to say that November-April was one very long stint of solo farming because I had nothing else to do. Furthermore I game maybe 10-12 hours a week, and a little more though the holiday period. I'm not bored of factions yet (even though I've only one character yet to complete it) but come November-December (I know 6 months is October but I think it will be closer to xmas before we see Nightfall) I think I will have probably retreated to the desert to farm more hydra, and consequently be becoming bored.
We got a year from Prophecies - Factions. However as someone has already pointed out, there were 6 "new" professions for us all to try. In fact the game was new, we had to learn it, Anet had to hammer out the little bugs that didn't crop up in beta, they had to learn new ways to make the cucrent engine a little more flexible.
So then when we got Factions, we ALREADY knew how to play the game, yes it was shorter, but WE made it even shorter because by the time it came out we had perfected our characters and preferred classes. Certainly we had to hammer out the details. Those who made it to the endgame in the first two weeks of release (we rushed something shocking) will remember their first encounter with Shiro often being ridiculously frustrating - at first. Now, however, the fight is simple, as we know how to do it.
I've no doubt that, with Nightfall, people will once again be able to finish it in a week, and people will (no matter how many missions there are) complain about the length. The onus is actually on us to make it fun (and in many cases) longer. If we rush though the game of course it is going to be short. Factions is a trade off between missions and quests. There are so many more quests than there were in Prophecies, something which I personally LOVE. In Prophecies the mission line was longer and there weren't as many quests. I generally hate missions, because there are times when you have little choice but to pug it, and pugs (more often than not) make missions unpleasent.
Anyhow, I'm getting a little off-topic. Is Nightfall too soon? For me, no. In three months I'm going to have very little trouble finishing what I want to finish and then probably move back to farming som cash for the next chapter. What I've learnt from my Factions rush was that the game is much more enjoyable if you take and do at least SOME of the quests, instead of rushing headlong though the missions. Remember that the team has been working on Nightfall for at least a year. Before you say a year is too short, remember that the hard part, the game-engine, doesn't need to be reinvented for the game, so they actually save themselves an awful lot of time not having to program and then EXTENSIVELY test the engine. Most of what they will worry about will be creating new skills and balancing them, and adding content.
/random rant
The apostrophe is indicative of a contraction or of ownership and NOT OF THE PLURAL (more than one). I am so sick of it being used as such. Since I know that most of you are US players, and English is indeed your first language, please learn to use monks (more than one monk) and not monk's (whatever it is belonging to a monk). Without the apostrophe, it's acutally quicker to type
/random rant