When you get a certificate, it has an expiration. This is necessary to avoid having to keep around revocation data forever, and so that old keys can't suddenly come to life. People using keys need to renew them before their expiration date. This renewal can be simple though. Getting an E-mail address key is simple to start with, and just involves mailing a request for one.
Renewal can work the same.
In fact, renewal of even more powerful keys can still be done by E-mail, as long as there is a challenge with some delay to assure the proper owner is aware of the renewal. I expect ordinary keys might be set up to last 6 months to a year. Anybody could post, as anybody. Anybody could cancel. Moving to a verified system simply reduces the number of people trusted.