Another example (and probably a better comparison than Bette) is Barry Manilow. His Hot 100 hit singles dried up around 1983, most likely a casualty of the Thriller/MTV era you mentioned above. His 1981 album If I Should Love Again was his last album to make the Top 20 until 2002's Ultimate Manilow compilation hit #3. During the 21 years in-between, he released 11 studio albums, only 3 of which peaked at #40 or higher. Then, between 2006 and 2011 he released FOUR studio albums that made the Top 5 (including one #1) and one that hit #7. His Vegas show also does huge box office...A "Manilow" career trajectory is what I truly believe Richard and Karen would have had if Karen were still with us. They would probably have never had another Hot 100 hit single (although they probably would still have hit the AC charts regularly), but they would have continued to release albums every year or two that sold enough to keep them under contract but probably didn't climb too high on the charts. Then at some point, with the right combination of timing and marketing, they would have become "cool" again enough to snag a couple or three big selling and high charting albums.
Great points, all, Actorman. In fact, I think you make a sound argument, particularly the Manilow analogy. I could see that being the case for Carpenters. Manilow, no matter the musical zeitgeist (i.e., he's survived disco, new wave, dance pop, hip-hop, grunge, and the current deluge of 15 year-olds currently dominating the airwaves), never gave up. I perceive that K&R might have had the same level of commitment to their careers, hanging-in there through the lean years and enjoying the inevitable resurgences of interest vis-a-vis the well-placed movie theme song and/or flukey hit album (to wit, Manilow's, Greatest Songs of the... series). Thanks for your post!