Now that the gnome-keyring-daemon implements SSH agent functionality and also supports 'auto-destruct' of keys, it is possible to specify maximum lifetime of added identities (SSH keys). Unfortunately this can only be done with the 'ssh-add -t X' command, because gnome-keyring-ask that pops-up when the SSH agent is contacted does not prove an option to set the lifetime of a SSH identity.

The solution would be to add a checkbox and a textbox to the gnome-keyring-ask password dialog for entering the lifetime in seconds or at least having a gconf option to specify the default lifetime of added SSH identities.

Additionally the password dialog could also contain a new button "Allow once" (now I have "Deny" and "OK"), that would be something like setting the lifetime to 0.