Thanks for helping out, Greta!
I totally agree with your 'method' because I do that to. I think music goes in trends, like most things in pop culture. I've noticed these same cycles in Production Music, even despite the broader ranges of creativity. Perhaps a client is wanting more "pop" sounding tunes so the artists / composers might try including tracks with a more 'commercial' sounding, pop-py appeal, etc.
Btw, I'm not knocking how many of us arrive at deciding the time frame of a particular LP. Sometimes the best way, the only way, is an educated guesstimate.
I was mainly wondering if somebody had a different method than mine. If Library knowledge is like a swimming pool, my expertise is more in the shallow end
Thanks again for your input!