Why not increase the bytes one by one and check which address you needed to update?
For example, you have 5 EEPROM bytes:
20 20 19 19 19
Next to increase is the third (address 2) so you know the setting now. Next update you make it
20 20 20 19 19
to index to 4 etc.
This way you only change 1 byte at a time. Aka you have 100k5 = 10 yotta cycles = 2,85 zetta years 
But indeed, with a single byte you already have 30 year.