Request Expiration Period

How long the request is valid from the time it was created. When a request has expired, it is no longer possible to process and a new request has to be created.

Approval Expiration Period

Used for Non-Executable Action Requests and specifies the period from the time the last administrator approved the request until it is no longer possible to execute the request's action. See Two Different Approval Requests for more details about Executable and Non-Executable Action Requests.