Provide a facility to allow a user to 'trust this computer for X days' which would mean that at login they would not need to go through the 2FA process again for the specified number of days.
This could be done with a check box on the 2FA form allowing the user to select this. 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 (set as part of the SphinxConfig would be reasonable) for subsequent logins.
It would either mean storing an identifier on the computer or to read some machine identifier.