How often do you wash them?
Edit to add: OMFG a 13 year old girl just called me to tell me that she found my wallet outside (everything still in it!) my job and is going to return it to me tomorrow. I thought I'd just left it in my cubby at work...I am in total shock right now. I'd really like to give her a thank you, but I am totally broke. Any ideas on what I can do?