Access Token invalid error

[Anonymous]

We are attempting to use the REST API to create leads in Marketo from a form hosted outside of Marketo.  

We have created the API Only User and Role, and then setup a Custom Service for the REST API.  

When we generate an access token for the Custom Service though and then attempt to submit via the API, we are able to get a couple of tests through and then start getting an Access Token Invalid error:

[{"code":"602","message":"Access token expired"}]

Does anyone know if there is an expiration on the access token, or if we are using the wrong access token for this setup?

[SanfordWhiteman]

There certainly is an expiration -- expires_in is sent back with the token.  This is noted in the docs.

I would also reconsider using the REST API for this simple form proxy pattern.  It limits you to 10,000 form fillouts, whether malicious or legit, per day.  (And that's assuming you aren't using the API for anything else, ever.)