How could he have figured out the exact day when it hadn't happened yet,. I'll grant you he knew 30 years and could have made precautions, but I got the impression he was trying to avoid them.
I think you're all missing it. Maybe I'm wrong, but my impression was this:
Prior to the Rainmaker, a Looper could count on a 30 year retirement from the date of killing his old self.
AFTER the Rainmaker, a Looper could not. The Rainmaker was closing all the loops, regardless of the 30 year timeline. That's why all the Loopers were closing out and Joe was pretty much the only one left. Don't you understand? Old Joe couldn't have predicted when his loop would be closed because the Rainmaker was having all the loops closed as soon as possible.