By default, Verify PIN codes are valid for 5 minutes.
If desired you may specify a custom PIN code validity period using the &pin_expiry parameter. This parameter value specifies the time in seconds for which the PIN should remain valid from the time that it is generated. For reference, this is the same as the request being received and the first attempt to deliver the code being triggered. If unspecified, it defaults to 300 seconds. Range: 60 - 3600, both inclusive.