A week before Big Phil and Tony got their P45s, Garry Wilson celebrated ten years in charge of Eastbourne Borough. During that time he's taken the club from the Sussex County Leagues (starting at Division 3) to the Conference and is still in with a chance of making the playoffs. And over at Soccerlens, I've done a slightly longer version of the remarkable rise of Eastbourne.
Interestingly, they've only had three managers since 1983. Chelsea and Portsmouth may want to take note.