It has always surprised me that at their highest point the material suffered. Their concerts were still sellouts so the desire for them was still strong.
Craig:
It's been noted in other threads over the years that it was, in large part, the touring that helped kill the recordings. Richard simply was too busy, too stressed, and increasingly too under the influence to write at his best level, and to make the best choices of material and arrangements as a producer.
Also: Carpenters' concerts being sellouts needs to be put in perspective. Looking at their touring schedule, it's a lot of 5,000-seat or smaller venues. In 1975, the Eagles sold out the Fabulous Forum in L.A. That's 18,000 seats. Elton John did Dodger Stadium for two nights in a row at 55,000 people per night. Sellouts have to be measured against the size of the venue. Put in that perspective, it was clear that the Carpenters were at the "solid corps of die-hard fans" level and not a lot more.