According to particle doc:
For security purposes, most access tokens will expire after 90 days. Certain access tokens can be specifically set to never expire, like the one you can find in the settings pane of build.particle.io.
You can list, create and revoke tokens in your account using the command line interface.
Also according to Cloud API doc it is possible to generate non-expiring token. I can put together a separate web form for generating such tokens, please let me know if this is needed.