How many artists from 1913 can you name?
Cliff can always record it again 50 years later, promote the new version, and get another 50 years exclusive. If McCreevy's theory is correct and the artist is the important person in the creative process of making a record, then their new recording will sell and they'll have created jobs and business in the record industry by making the rerecording.
So even if we ignore the fact that old recordings don't sell, are not worth promoting, and Cliff Richard will not live till he's 120, even then it's not a good thing to let him sell the same stuff forever because it displaces new works.
Gotta move on. Can't keep doing re-releases and best of's forever. Even if they need a little coaxing to go and re-record the tracks. Cliff should get off his lazy butt, refresh the tracks and rerelease a refreshed CD to start a fresh 50 years.
"while most of us have no idea who wrote our favourite song, we can usually name the performer."
Funny, I don't remember any of the performers from 1913 (2008-95 years), I bet you can't even locate their recording contracts or trace legal ownership anyway. Since it spans more than 1 persons lifetime, it's not possible to take legal testimony from people over contracts because those people are dead.
And I'm pretty sure in 50 years time I won't remember the artists names of today either, I'll be dead too you see.
You gotta be realistic about these things. 50 years is plenty, if it was worth anything then Cliff would be rerecording and promoting and performing, not mulching away. You don't want to give them a reason to resell the same recordings over and over again 50 years from now, and don't want to create a lawyers market where lawyers try to argue over ownership of historical recordings from long dead artists.