Re: I'm not sure it's quite that easy...
Exactly.
And whilst I am no crypto expert it should not be difficult to enforce expiry and deletion for publicly available keys across all key servers. Yes keys can be revoked, are they deleted from all key servers? (seriously I dunno) I could revoke one to find out or google, I will after I post.
Once an expiry date is reached one chooses to renew or revoke/delete public key.
Just a thought.. Always up for an education though :-)