To be honest, I was a bit off in both directions. I thought BN was a bit later - ca. 1980 - and that ND's career began a bit earlier. (1962 or 1965, depending on how you choose to count.) In any case, I'll stand by the "ten or" half of the original phrase.

Chronological details aside, though, it seems to me that the Diamond of the mid-seventies had shifted well towards the pop end of the rock-pop spectrum, with a smoother sound but less of an edge. Subjective, I'll admit, and of course YMMV, but that's my impression.