I have seen a lot of info lately on the migration away from felt soles due to the transmission of micro-organisms that they permit. I haven't seen any mention of the pros and cons of convertible boots for the same problems. Is there any issue with all of the nooks and crannies that might carry things along? I'm curious, I own a pair a of Korkers and I'm debating whether to invest in additional soles or moving to a new boot. Any opinions here as to which would be better for the environment?