Hemp is known to get little holes. Cotton is probably best. Elastic wears out, so probably prefolds. I don't know off the top of my head whether PUL wears out or lasts a while. But if you have a nice stash of prefolds, covers won't be that expensive to buy and you can always buy used off the TP for really really cheap! I have prefolds that I'm using on Sara that have been through BOTH my neighbor's kids and are still going strong. They are just run of the mill chinese prefolds too. So I KNOW they survive well in rubbermaid plastic storage containers away from bugs and dirt and water.
Meg
Meg