How often do you replace your mirrored visors?

I know mirrored visors are high maintenance and are far less durable then their tinted counterparts but I've had my visor for only about a month and it's already getting scratches and not small little scratches when looking at it closely. They are large scuffs of the finish itself rubbing off. from a rock but when got home today and looked at my helmet noticed another but it seems more like the finish is rubbing off but l'm not sure how that would happen because haven't washed it for about a week and im very cautious when carrying it around or setting it down. How often do you guys replace your mirror visors? Excepted to get at least one ridding season out of it.