Or at least your email.
Company-wise, we have a policy of three year retention of mail; indefinite for certain special items. Personally, I try to keep things trimmed to the last year at most. I wish more people would set themselves some kind of purge schedule for mail. I’m trying to move someone with 140 gigs – that GIGS – of mail spread throughout their corporate mail. Do you really, really need a copy of that mail you sent six years ago? Or some piece of mail you received four years ago that references something that no longer even exists?
Figure out some kind of policy for your mail and make it as common a chore as vacuuming your floors or changing your bedsheets. Your mailbox (and your mail administrator) will thank you.