From 2009-2014, it was a 2 year cycle with SOME updates the second year. 2015 was a 1 year cycle, then back to a 2 year with 2016-17. I don't know why. Last year, there was an "edited" PDF that came out with the 2017 updates. I suspect they will continue with that, so essentially, if you download PDFs, there will be a new one each year where the second year only has minor changes.
For me, hard copies are essentially obsolete. I'm going to get a football only tablet this spring to take with me to all training sessions and games. I will put the rule book on it and have direct links to training stuff and videos. Anyone have any suggestions for a cheap(er) tablet? I've only used iPads and don't really want to take mine to a game.