The dark colouring on rings will eventually go back to silver where it gets rubbed. This leaves the deeper sections staying dark giving the band a beautiful rugged appearance. If you like the overall dark colour though it can always be re-oxidised back to the dark tone whenever you like.Over time oxidation will wear off. In some rings it wears off quickly - in others, it comes off slowly, changing the appearance of the ring. Skin oils, perspiration and soaps will take off the oxidation more quickly.
If the colour has faded to much for your taste then you can re-oxidize at home using eggs.
A good example of how to do it can bee seen in this video here - https://jewelrymakingjournal.com/how-to-oxidize-sterling-silver-and-copper-with-boiled-eggs/