my personal view is that for casual listening for pleasure
a good single artist or band CD
should achieve all it needs to communicate effectively
within 35 - 45 minutes.
Anything longer usually struggles to maintain listener interest,
relying too much on sub standard padding..

However, a well programmed multi artist compilation
definitely justifies filling the full 80 mins format.

Same applies to lovingly compiled single artist/band
complete recording career historic commemorative boxsets....