I might have missed this, or it needs to be a feature request.
It would be great to have the facility for a user to check a box saying 'trust this computer for days'. This is quite common on sites where 2FA is used (like the UK HMRC site).
If checked and the 2FA validation passes then the user would not need to complete the 2FA for the specified number of days (part of the SphinxConfig maybe) for subsequent logins.
It would either mean storing an identifier on the computer or to read some machine identifier.