Choosing a storage class is a bet on when you will read the bytes again. S3 Standard costs $0.023 per GB-month in us-east-1; Glacier Deep Archive costs $0.00099. That is a 23-fold difference for identical durability, and the whole decision is which number your access pattern deserves. ...
A credential expires only when the system deciding access checks an applicable deadline. Writing an expiry date in an inventory does not change what a database or API accepts. A short lifetime can reduce the period during which a stolen credential starts new access, but its effect depends on the authentication mechanism and on what happens to sessions or other credentials already created with it. ...