It was those damn picture threads.
Congratulations. 
I have to admit that when I got to 39900, I did do that on purpose, just as I had when I got to 38900 and 37900 so long ago; I went to the files on this computer and yanked pictures of primitives to post, so as to hurry up and get to the next thousand.
And then when one reaches that plateau, one eases up and slows down, until inevitably one finds one has crept up again, and so time to do this again.
It's taken about a year and a third, on average, to make 10,000 posts.
When I first came here in January 2008, Crazy Horse was the most prolific poster, and as he's a fine man, I wanted to follow in his footsteps, and so took off after him.