The truth is many if not all of the manuals don't need to be updated each year. For this reason what if SW just stop putting the date on the cover of manuals?  There could still be something in the cover or the serial number/product ID but it just doesn't need to be obvious date.  We are still going to buy manuals so I don't see any loss of revenue by this change.

Switching to a two year cycle on manuals that really don't have any huge software changes might balance the load and afford time to get the manuals that really need revisions done in time of release.  For example, SW 2014 was released 10/7/2014 and there is still no 2014 routing manuals 5+ months later as of this post.  If there was no date on the cover of the manuals the students would not know any better.  In the case of minor changes between versions you could have a 1-2 page PDF that can be used for instructors to be aware of any differences or even print and handout.