Daily since 2004? Is that just weekdays? What do you mean by "pre-written"?
When ENWorld went down (was that early 2007 maybe?) and we lost threads, I switched to daily.
Yes, that includes weekends.
By pre-written I mean I've written them all. It's done. 60+ chapters of MS Word docs for Arcanis. Modern is currently up to date (but ongoing).
Here's how I do it: right after the game, I spend the week writing the story hours. Sometimes this takes a couple of weeks -- especially with the Modern story hours, which is usually two or three smaller stories. Then I send them to my players.
The players in turn correct them for errors. I forget things sometimes (easy to do when my son isn't sleeping, I'm sick, my job is stressful, or I was caught up with one part of GMing while the players were talking). Sometimes I edit the events in such a way to make them cooler or fill in the blanks, and the players don't agree with the change so I have to change it back. There was recently a huge blow up over the depiction of a character using charm person (I showed it as street hypnosis, he wanted it as a more FX effect) -- so there IS a review process of sorts to ensure accuracy.
Then I edit the whole thing one more time and post it once the story hour gets to that point.
Because I write each story hour as a chapter, broken into smaller scenes, the two story hours take a very long time to play out. I don't mind this. I also post a summary of it to my blog. This has skyrocketed my Google rankings, as Google loves active blogs. As an experiment, if you type in "Arcanis" and another word, like "lizard" or "legionnaire," the thread shows up in the top 10, and sometimes even #2. Heck, "Modern" and "Delta Green" causes the other story hour thread to show up in 4th place.
What probably helps is that I advertise new installments everywhere. Gonnes, Sons, and Treasure Runs was regularly advertised on the Living Arcanis Yahoo group, Yog-Sothoth, and the Green Ronin forums, depending on which adventure we were playing. The Beginning of the End is advertised on the Spycraft, Monte Cook (d20 Cthulhu), Yog-Sothoth forums, and the Delta Green Yahoo mailing list.
And then there's my new column on RPG.net about my gaming group,
which is a behind the scenes look at the Beginning of the End story hour.
So in other words, I actively cultivate links to the story hour beyond ENWorld.