Epic levels are when player characters are among the greatest. Who they are is now epic, what they have or use in none less. They break from the confines of what's known to mere mortals, and their most powerful friends, allies and foes are either gods or avatars. They talk to the forces of nature and planes, they weave the greatest of spells and slay the monsters that roam not only space but also time and alternative realities.
Epic should be epic. It's what the players worked for, it's what they deserve, and if you're a Game Master / Dungeon Master / Storyteller, you should reward them for playing the campaign with you all this time. Do that by bringing the mindboggling adventures and the ultimate rewards.