Time it seems to revoke it so that I never have to worry about it again (and before I forget the passphrase for good). Revoking a key essentially puts an end date on the key, it says any use of the key after this date is definitively invalid. Luckily revoking a key (that you can remember the passphrase for) is relatively simple:
gpg --edit keyWhile I was at it I started to wonder about losing keys and how one guards against total loss of a key. The received wisdom is to set an expiration date on your key. These may be extended at any time, even after the key has technically expired, assuming you still have the private key. If you do not then at least the key will automatically fall out of use when it expires. Adding an expiry date to a key is also pretty simple:
gpg --edit-keyNote here I am setting the subkey (or keys, key 1 and higher) to expire in a year, and the main key to expire in 18 months.
gpg> key 0
Key is valid for? (0) 18m
gpg> key 1
Changing expiration time for a subkey.
Key is valid for? (0) 12m
At least now the keys I care about are protected and those I do not are put out of use.