Instruct: Retrieve semantically similar text.
Query: But for them, they get the benefit of the longer term if you don't apply it to an existing copyright. I mean, if you say you need 70 years because of changes in the economy to encourage works, you grant 70 for the future, but why does that, making that apply to somebody provided him?
Longer term benefits come if you don't apply the existing copyright.
Copyright Clause is not the main focus of the question.
limited times is not up for interpretation 
Life plus 50 or life plus 70 is different than a copyright
Sometimes it might remain unclear.
copyrights have their value for life.
There is a possibility that the person will not be instantly available.
There are copyrights.
The writer has a copyright that is going to expire.
copyrights never lose their value
It might sometimes remain unclear.
Copyrights aren't for forever.
The holder of an existing right may benefit the public by continuing to have that right for an additional period of time.
this agreement takes effect over many years
The argument may imply that the act has impeded progress in some areas. 
Using a prior decade is not necessarily an error.
copyrights have value infinitely.
money is used in various ways
This piece of advice is speculative and makes certain inferences about the reader.
an unlimited time would violate the Copyright Clause, which is bad
This case has gone on for quite some time
Copyrights lapse eventually.
experts predict the economy will suffer
70 years is too long for a copyright to last.
the economy is in a downturn