I think we're missing the flip side of this coin. I haven't seen a stat on how long you keep coach / QB together after a SB win.
For example, assume we had won it in 2003. How long then do you keep Delhomme / Fox together?
What about after a SB loss? For example, the Marv Levy / Jim Kelly Bills. The first four years went: 4-12, 7-8, 12-4, 9-7. The next year they were 13-3 and lost the SB. Do you break up that combo? They went on to three more SB's, and lost all three, for an NFL record four SB's in a row lost.
I think the consideration should be: Are we qualifying consistently for the playoffs (say four out of five years)? If yes, ride with what you got. If no, try something else.