Make it epic. I've never done epic. Post-twenty, or close to it. That's where my thinking is right now. I may change my mind (and probably will) but it would definitely be different. I have never done epic before, or anything remotely close to it. Highest level I have ever run for is 10.
Though there are reasons why I have never run epic, and why it still might be a bad idea. Epic is hard; there's more to keep track of, more powers to take into account, more stats to keep track of. Combats last longer, and are more complicated.
Of course, I don't plan, at this point, to be running a combat heavy game. There will be some combat--this is Dungeons and Dragons we're talking about, but like the first one, I expect that a great deal of what the players accomplish in this campaign will be accomplished without much combat.