I have the Brooks Saddle cover. Got it for $10 new on eBay. Haven't used it yet. I notice that the way my Brooks B17 supports me changes as it warms up on a ride. I have the saddle tilted forward a bit for this reason. As I ride, the back part accommodates itself to my sit bones and I'm not pitched forward as much. Even with a rain cover, it seems high humidity will change the characteristic of the leather on a ride. From what I read online, it shouldn't shorten the life of the saddle.