User blog comment:Jopjopjop/Volume 18 Spoilers/@comment-25072311-20140621062142/@comment-24910433-20140621063936

If you put into consideration that they'll go at least until Issei becomes a High Class, which Sirzechs said was roughly 2 years away at the end of Vol 7, and if there were no big timeskips, then that would mean it's not even halfway done yet.