Is it necesary to use eeprom? Maxim sells (samples!) some very nice 2Mx8bit battery backed sram in a simple pdip package, with the onboard battery rated to 5 years. You'd be able to leave the "rom" in lower ram (say) and just erase everything above it on boot up. If you're worried about the 5 year limit you could always have a secondary trickle battery that only kicks in when there's no other power and only powers the ram. You'll probably need such a battery if you're going to include an RTC anyway, which might be handy.