does an authorization to release educational records for an application a school last indefinitely?

the text is:

“By signing this form, I authorize all schools that I have attended to release all requested records covered under the Federal
Educational Rights and Privacy Act (FERPA) so that my application may be reviewed by the Common Application member institution(s) to which I am applying.”

Does that authorization last forever until I revoke it? Does it give a carte blanche to my former schools to release information without my knowledge?

While no specific time limit was given, it does state “so that my application may be reviewed”. So presumably, once they have completed reviewing it and notified you of acceptance or rejection by the school, they are no longer using it for the purpose you authorized, and so should no longer use your records.

Yes, that is the intended purpose – that your past schools can send copies of your records to the school you are applying to. Those prior schools could notify you, but there is no requirement to do so.