I have an off-white pair (slightly gray-ish, but very light = almost white) and I have to say I'm impressed with how white-looking they have remained. I don't clean them and I don't baby them. They're the only pair of road cycling shoes I have. If you stare at them, you can tell they're not even close to blemish free. BUT, they get the overall impression of being pretty damn white.
What's the line from Shawshank Redemption: "How often do you really look at a man's shoes?"