If not then what is a good way to archive mail? Ideally I'd like something where I can say "archive all mail older than X" or something like that. I am using maildir so I guess I could just use shell commands to find all the old files but a method where I don't have to think too hard or read a zillion different man pages would be better ;-).
One trivial method I used to use was to create a new mailbox for the archival (eg, WLUG-03) and move all messages with that date into that folder. Depending on which brand of maildir you use, this can be fairly easy to arrange from the shell , and is easier still if you don't mind using a GUI client so you can just highlight the whole lot. Otherwise, it seems like something that someone else will have done already, have you checked freshmeat.net ?