From Andrew Hussie's long-deleted Formspring on 18 Jul 2011:
MSPA is the longest web comic on record, in terms of update quantity. It accumulated most of this content in about 3 years. Now consider that the second comic on the list is approximately THE OLDEST WEB COMIC IN EXISTENCE. It dates back to 1995, which for all intents and purposes was the year the internet was born.
There are of course some mitigating factors. Most MSPA updates are a single panel, with some accompanying text. But there are some counter-caveats which make this a bit more difficult to process. There are several hours of animated Flash footage mixed in with the updates. There are several more hours of interactive gameplay. Each Flash instance occupies a single update. Many updates are accompanied by several pages of dialogue. Some of these individual conversations would take up 50 pages worth of speech bubbles in a graphic novel. The total word count for MSPA likely exceeds most of the comics on that list, or possibly all of them. It wouldn't be surprising. Homestuck alone is over 300K words. Again, this effort was compressed into the last 3 years, while most of the other comics date back to the 90's.
What does this mean? Here is what it means.
Let's imagine MSPA was distributed more like a "normal comic". Where, even with a healthy update schedule of 7 days a week, you still only get one new thing to click on. One update per day. It could be a simple panel with a silly gag and no text. Could be a panel with 10 pages of dialogue beneath it. Or it could be a 3 minute flash animation. All are things that appear in the archive in good supply. Distributing one such thing per day, as the designated "product", would be a completely reasonable policy. If that were the established pattern from the start, nobody would think it was remotely inappropriate, and nobody would ask for more, in the same way that nobody ever demands that Penny Arcade update 7 days a week instead of 3.
If that were the case, MSPA would now have 16 years worth of content.
So what does THIS mean??
It means, given that I started 3 years ago, I could take a 13 year break starting now, and at the end of that break, MSPA's lifetime rate of production would still manage to make the lifetime rate of most other comics seem underwhelming. This is literally, actually true, even though it sounds like a joke. There is statistical evidence to support this, using the only data that matters, which is the existing work of peers in the same field.
So if some twerp who's never put a stretch of hard work into anything aside from grinding for levels in WoW all weekend decides to get on my case about slowing down, I think I'll just start whispering "13 year break..."
13 year break.........
13 year break............................
13 year
break.
In fact this number was not quite right. It's true that MSPA had accumulated most of its content in the previous three years - to be exact, since starting Problem Sleuth three and one-third years earlier on 10 March 2008. But there were only sixteen years of pages if one also includes material from the still earlier stories Jailbreak and Bard Quest, which were written/imported onto the site four years previously - the first page with a date is 12 June 2007.
Either way it worked out to more like a 12 year break than 13.
I used to calculate the break based on all pages starting 2007-06-12, but have since persuaded myself it makes more sense to base it on PS and HS pages starting 2008-03-10 - the start is more clearly defined, it fits better with Hussie's "about three years" of more rapid production.