Expiring OAuth token

Yeah so that’s what the OAuth tokens are designed to to. They are meant to be used to keep tokens for REST asset use. The rest assets are designed in a way that they can try and make an API call using the token, and if it’s expired, it can try and request a new token using the refresh token ID which is normally supplied by the API, so you don’t have to worry about it at all.
Have you got a link to the API integration docs for Sringshare that we can look at?