The token expires after 30 minutes. The 30 minutes is the time range from generating the token until asking for the status of the transaction.

However, a pending transaction will time out sooner: When a user is redirected to an external payment system like paypal, but doesn't return from there, the first timeout will be the one from the external payment system, which happens usually after 10-15 minutes. If no timeout notification arrives on our servers, our system will automatically set the pending transaction to timed out after 18-25 min.