Here we go. Only 250 miles left to ride! Yea. ...miles to go...promises to keep...
(The initiated among you know that besides being my motto, that snippet of a Frost poem was the inspiration for the name I chose for myself.)

Ed Pavelka, the co-author of Long Distance Cycling, and the editor of RoadBikeRider Magazine says that an effective strategy is to ride a negative split - ride the first half conservatively then the second half more quickly. He says it's "like a carpet unrolling". I'll give it a shot. We'll see if it works.