I don't track them, in general. I do, however, use them for a few rare home-brew mechanics. For example, my suffocation/drowning rules use CO-based RRs each round. If the RR fails, the margin is subtracted from the character's EP (I always start with those at full.) When they run out of EP, the failure margins come off of a stat, and when a stat reaches 0, they are dead.
Using HP didn't make sense, since a wizard and warrior can drown equally quickly. Doing it this way, the character may need to lay there and recover for a few minutes, if they only lost EP. If they lost stat points, half of that loss requires magical healing, the other half recovers at 5 points/day of rest.
Other than that, if a battle is going on for more than 10-20 rounds (maybe once in my gaming life!) I might start to tally up the EP cost for the fighters.