IMHO, i would avoid to write too much to the EEPROM and avoid to reduce his lifetime.

2 Possible solutions:

1. write to EEPROM when you remove the key from the ignition switch. You must have a switched 12 volt and a constant 12 volt routed to your cluster..

2. Write to the EEPROM only when the battery is disconnected. For that you'll need to add some extra hardware but not impossible.

Option 1 is still good enough to me so far