here in Texas S30V and similar SS gets coated once a month. Tool and high carbon steels get it a couple times a month.
Texas is hard on knives especially when you're carrying something close to the body.
As far as stored knives go i've never had any problem with rust, but i still coat them every few months.
it will wear off even on lightly used knives...but i haven't found anything that works better in the Texas climate and i've tried a great many things. S30V starts to pit every week if i don't stay on it. they only steel that i can use here that doesn't need it quite so often is Duratech 20CV (great steel all around!!!). D2, 3V, 1095, 5160, M4....they all rust within a day or two of carrying if i don't coat them daily.
hope that helps