For checkout, paymentlink, and redirect orders, sets the number of days the link to the payment page or FastCheckout page is valid.
The link lifetime begins when the order is created, or the link is generated. A session_id is returned in the payment page URL.
If Second Chance is enabled, we recommend a minimum lifetime of 48 hours. Second Chance emails the customer 2 payment reminders: 1 hour and 24 hours after the order is created. If the lifetime is less than 24 hours, the link in the second email is no longer active when the customer receives it.
See seconds_active below. If seconds_active is also set, seconds_active is used. If neither is set, the default is used.