Can I assume anything about the state of the EEPROM when I open a brand new Pro Mini? Would it be set to all zero? Or should I run a clear EEPROM sketch against each board prior to loading my code?
If I remenber well, all EEPROM bits are valued 1.
Since there are many sources of Pro Minis and other Arduinos, it is probably best to not assume anything. In theory all the bytes are set to FF (decimal 255), that is their erased state. It may be best to initialize to the values you want.