Q:

How to check foursquare api oauth token expiration?

I'm looking for documentation that explains following details:  

what is the default foursquare api oauth token expiration?  
how can I check expiration for any given token?  
how can I extend time to live for oauth tokens?

Thanks

A:

Apparently they don't:
via Foursquare Oauth API docs

Access tokens allow apps to make requests to Foursquare on the behalf
  of a user. Each access token is unique to the user and consumer key.
  Access tokens do not expire, but they may be revoked by the user. If
  your application doesn't require connecting with Foursquare users, you
  can skip directly to Userless Access.

