From 1st to 7th levels characters advance normally. After 7th level, players gain a new feat that they qualify for every 5000 xp they gain after 7h level, to a maximum of 20 post-7th level feats.
After 7th level, denote your feats as follows: a 7th level fighter with 3 epic feats would be notated as "ftr 7/E3."
For every 5 feats gained after 7th level, you are roughly one level higher for the purposes of facing challenges, and that is roughly how I'll gauge xp awards.
