Another trick I have seen to save EEPROM life:
It is used in an Arduino Antenna Rotator, is to monitor the 12V via a voltage divider and Analog port.
When the voltage drops maybe 1V below "normal", as seen at startup, write settings to eeprom only then.
When you power off the radio the 5volt regulator + input capacitor should hold up the Arduino for just long enough to catch the voltage dropping and write the last used frequency to memory....
73, Nik, VK4PLN
Nick VK4PP