I believe that kydex sheaths are just about the best protection you can give a knife. The material takes a lot of abuse from the weather, as well from eveday bums and bruises. Even so I would still recommend taking it out daily for a wipe down, as it can sweat some and you want to keep it as clean as possible,and the rust shouldnt be a problem. Leather is still the best material because it will form the best around the knife. It is the best looking material because you can do so much with it. As far as cleaning goes, I would still try amd wipe down tha knife daily. As far as rust is concerned, the skies the limit. I use a no.1200 grit paper, to get the rust of, if its not to bad, however croakus cloth works well too. I dont use a polisher much because I dont want to mess up the blade too much as Im not too good with a polishing wheel.