We're looking at 30.5 posts per day, on average. Assuming he sleeps 6 hours a day, works sometimes, eats, poops and pees and so on, I think that's about 10-11 hours of available posting time. Let's settle on 10 out of his 18 waking hours, which is pretty conservative. So, a little over 3 posts every EAPH (Estimated Available Posting Hour.)
With about 21,900 left, we're looking at 717 or so days. I'll say June 1st, 2016. I think he accelerates it a little towards the end as people begin throwing out congratulatory posts which he graciously responds to.