Disc space? Well... if there are 50 thousand monsters in game, and each
monster "remembers" only players who have actually killed that monster let's
say the previous 14 days (or whatever period which after the monsie would
again give "full" exp) - I don't see the space needed a big issue. It would
all cook down to a 4 column table: monster_id, player_id, kill_count and
timestamp_last_killed_by_player. Battle code should take care of calculating
exp tune, in addition there would be a need for a batch job running at
boot-time to clean up the table (based on how long time for a monsie to give
basic exp to players).

Updates on an SQL database are costly, and you would be
inserting rows and updating almost constantly. Aren't
the monsters hard enough with the new spell tunes
already?

Sorcen