Inspectlet defines a session the same way Google Analytics does: sessions are consecutive pageviews and a new session is created after 30 minutes or after 24 hours.

However, if you need to manually trigger a new session before the above conditions, you can call:

__insp.push(["resetSession"]);

resetSession needs to be called before Inspectlet fully initializes, so please place this line in the same block as the main Inspectlet JS code.