It's life spiraled from a very lively center, quickly became more infrequent, continues along in infrequency, and has yet to die.
1998: 1 Year in Japan
1999: 1 Year in the International Limelight
2000-2001: 2 Years of full-fledged support
2002-2004: 3 Years of extended support
2005-2009: 5 Years of fringe support (3 of which official, 2 after-market only: 1 after-market year in which Sega Direct was still open, 1 where it wasn't)
2010-2017: 8 Years of bolstered after-market support by diehards?
2018 has never been more important. Also, it will be it's official 20th Anniversary! Maybe that means 13 years of being full-on "retro cool" and being milked for all it's worth by a previously-unaware culture. Seems like awhile, but how long has NES had the status now?
Just having fun here. This all is very disputable and context-sensitive stuff.