From Google in September of 2013
, "Meanwhile, NPAPI’s 90s-era architecture has become a leading cause of hangs, crashes, security incidents, and code complexity
. Because of this, Chrome will be phasing out NPAPI support over the coming year."
Again, from Google, "Stable channel: This channel has the full testing of the Chrome OS test team, and is the best bet to avoid crashes and other issues
. It's updated roughly every 2-3 weeks for minor changes, and every 6 weeks for major changes."
I'd suggest reading https://www.chromium.org/developers/npapi-deprecation
for more information.