I sometimes think that the reason for the differing cut-offs on WTs and Awakes on WT-library (1950 for WTs and 1970 for Awakes) is the infamous 1969 Awake quote that says something about young ones never growing old in this system, encouraging them to neglect schooling, etc.
They've got a pretty perfect system set up that makes it easy for them to throw away the old literature anyways. All the literature is just the same regurgitated crap year after year, so if you go back 50 years you won't really have anything more (other than doctrinal flip-flops) than you would be able to get by just going back 10 years.
I'm interested to see if they start removing old stuff from the website too eventually. Now that would be telling.