Q: how does one run an epic level game?
A: very very carefully.

1: at this point your players are either a unbeatable master at one aspect (bluff high enough to lie to a god, hide good enough to be undetectable in plain sight, spells that destroy worlds, or make you invincible for an extended duration. BAB differences that either always hit, or always miss (sometimes both in the same party), AC that either 30's-40's or 80+ (always get hit or always don't get hit). And charge crits that deal more damage than players have hp.)

biggest thing to remember is that everything your players can do, you can do also (and the reverse is true too).
Don't rely on the hit points of a monster (you will always estimate wrong). End the encounter when it seems appropriate.


Be creative. The trick is not to outpower your players, its to get them to problem solve. How do they locate the invisible assassin, how do they kill the thing with 300 fast healing, how do they kill the monster without killing the princess (or kingdom) in it's belly ect.