title: Proper paradigm for refreshing OAuth2 access token
body: <p>I'm working with an API that uses OAuth2, provides an access token that expires in 3600 seconds, and provides a refresh token with it.  Originally, I'd waited for an API call to fail in a way that indicated the access token was expired and then tried to refresh the access token using the refresh token.  This has become problematic when the access token is expired and several API calls are made concurrently (each call separately triggers a refresh and most of the calls fail).</p>
  
  <p>Would it be better to automatically refresh the access token using the refresh token after 3600 seconds?  (Or 3599 seconds or 3601 seconds?)  Is there a different paradigm I should be using for refreshing the access token?</p>