Future of anonymity (short-term vs. long-term)

IMHO a remailer operator should *NEVER* reveal any identities, but I also believe very strongly that especially if you provide a way to post news articles, there has to be a way to send replies to the original sender. Thus a remailer must maintain mapping info. I like this. Does it make sense (and has it already been talked about?) to preserve the return information only for a limited time? dean