Lemme reiterate my views on storing knives in leather:
The better the quality of the leather the less chances of there being any corrosive salts left in the leather. The type of leather I use is top shelf stuff, I've got high carbon steel knives that rest in their sheaths constantly. But be sure of the quality of the leather, the cheap leather some mass makers use is very questionable.
Leather doesnt hold water. If your sheath gets wet you must let it fully dry before using it again, this can take anywhere from over night to several days depending on the temp and moisture in the air. When the leather no longer feels cool to the touch your pretty safe. A good quality leather conditioner is highly recommended.
Cheap leather will also loosen with time and use, will become spongy and floppy. Good leather will stay solid and soften slightly with time. Keeping the leather conditioned will extend its life considerably.
Get quality stuff, the cheaper stuff only wears out faster and you'll end up spending the same or more in the long run.
The same basic rules apply with kydex, a good sheath will last forever but a bad one will ruin a good blade.