I can think of ways to be vanquished much quicker than he did, especially if he's willing to be reverted to horcrux. Challenge Dumbledore to a duel and lose. Be seen doing some dark ritual, which then goes out of control, killing him. Hell, I'm sure someone as competent as Voldemort could have faked a prophecy about his doom.

If I were Voldemort, I wouldn't have waited on that prophesy until I needed to make an exit.