Well, I'm relieved.
I thought one of those late night spammers was going to get it.
I checked the count about once an hour all night long, and would have been on guard had it started getting close.
Maporsche nearly got it though:
But I was pretty quick on the draw. Once it got to about 6666660 I started refreshing the RSS version of the "new posts" page about once a second, and the moment it hit 6666665 I control-tabbed over to the next browser tab and hit the post button with the spacebar (the post button having been "selected" already so that hitting the spacebar would activate it).
I also did practice runs as the count started to get close, with the preview button "selected" instead of the post button, just to make sure that everything was likely to work smoothly.
OK so I'm a geek.
I'd originally intended to post it in this thread, but then I realized that it would be perfect for that other thread so set it up over there.