Rethinking my energy drain house rules

I dunno, I feel like they were a bit too fiddly and specific, maybe? I'm thinking it might be simpler to just do like my good pal Randall Stukey does in Microlite74. (Except for vampires draining CON because I maintain that makes the most sense and is also fucking cool).

Energy Drain: An attack that would ordinarily drain a character's level instead deals 1d6 damage and imposes a cumulative -1 penalty on all attack, saving, and proficiency/ability throws. If the penalty exceeds the character's level, she dies. 1 point of energy drained is recovered every L days where L is equal to the hit dice of the monster that drained the energy level.