I tend to keep pouches in the pouch they come in for a time, and then transfer them to jars. However, I use a fold-over fabric pouch with a liner if I want to carry a portion of bulk tobacco from a jar. I think the fabric or leather tobacco pouches, zipper or fold-over, are also a sort of fashion accessory, to dress up the pipe smoking process and personalize it. If you have a handsome leather tobacco pouch, I'd make a point of using it. I don't store leaf in a pouch, or not for long periods. Frankly, when I've forgotten and left the tobacco in a pouch it came in, or a fold-over, the tobacco gets dry but smokes just fine. Not best practice, but perfectly fine, though I don't advertise it. Pipe smoking is pretty much freestyle, and you get to do it your way.