Long term offline mail retention

[Jason L Tibbitts III]

I manage email (and practically everything else) for a medium sized
university department.  Recently I've been informed that we're adopting
a three-year retention policy for email.  We're allowed to keep things
for longer than that, so I'm not looking at forced expiration (which is
all I found when I searched the mailing lists for info).

Basically I'm just looking for a way to still allow me to use cyr_expire
with something less nuts than -X 1100 -D 1100 that still keeps the mail
somewhere.  (I'm honestly quite afraid of how long an expire run will
take three years hence.)  I'm thinking of hacking cyr_expire to actually
save the data off somewhere, then tarring that up to some less expensive
storage and destroying that when its time comes.

Any ideas?  Has anyone done anything like this?

 - J<