JMeller:
From what this n00bie has read, EEPROM has a specified life of 100,000 write/erase cycles.
I don't think that is necessarily as bad as it might at first sound! There is some useful background at
http://forum.arduino.cc/index.php?topic=282974.0
I just bookmarked without closely reading, but the first line of the first post suggests the EEPROM is to be used for its proper purpose, and the advice is from gurus who really do have practical experience.
Very useful info- thanks Nick.
A few ways to reduce data:
Date: don't store day, month, year. Store it as "days since epoch" where you can choose your epoch. This allows you dates spanning 256 days in a single byte; 65536 days (almost 180 years) in an int of two bytes. The same two bytes allow for hourly resolution if you're OK with rolling over after 7.48 years.
Floats: if you need two decimals, multiply the number by 100 and store it in an int. That way you can store any value from 0.00 up to 655.35 into a single int of two bytes. That saves half the space.