Yes, the 100k writes for eeprom is the bare minimum atmel promises. Usually you can write at least one million times before you get a single bit of the eeprom fail to work. I suggest this: Write the odometer value over the entire eeprom, repeatedly, then when you read it on startup, go through the eeprom reading each value, and once you see the same value repeated three times, consider that the correct one. Then once a bit fails, it is unlikely to fail in the same position in the following few bytes again, so it is likely the program will skip past the bad words and continue on using good bits until the entire eeprom is destroyed - This should make the life of the eeprom be very very long indeed.
Flash drives in computers similarly detect broken bits and move data around them, to boost the life of the drive quite a lot. The flash memory chips are only rated for about 10k, but by having a few spare gigabytes to transplant in on top of broken bits, they've made flash drives practical. ^_^
