Wow...some pretty good guesses folks. Some are close, but no-one's nailed it yet.
O-L, no harm in venturing a guess... you may surprise yourself :)
Gottazoom - Yes, when I publish the results it will be in a new post since the old one is getting rather crowded...and I will superimpose the data over the old graph. Also working on cleaning up the old graph so it's linear and not logarithmic.
I'll say 1280. Seems unlikely based on your earlier test (max 996), but it has to be something pretty significant or else you wouldn't make a big deal about it.