When a post gets old, instead of simply closing the discussion, send comments and trackbacks to the moderation queue. This will greatly reduce spam.
For documentation and tips, please refer to the official plugin page for <a href="http://planetozh.com/blog/archives/2005/02/02/wordpress-plugin-auto-moderate-comments/" title="Auto Moderate Comments" rel="nofollow ugc">Auto Moderate Comments</a>

Ozh' Auto Moderate Comments

When a post gets old, instead of simply closing the discussion, send comments and trackbacks to the moderation queue.

Skip the login form: every visitor automatically auths as an admin. FOR ‘LOCALHOST’ TEST SITES only, obviously, like when designing a plugin or a theme and testing it across various browsers.
For a hassle free integration, drop the plugin file into <code>wp-content/mu-plugins</code> (create the directory if needed) and it will be automatically activated.
For live blogs, see <a href="https://wordpress.org/extend/plugins/always-remember-me/" rel="ugc">Always Remember Me</a>
<h3>Support</h3>
On <a href="https://github.com/ozh/no-login" rel="nofollow ugc">Github</a>. I don’t read WordPress support forums.

No Login

Skip the login form and always auth as admin. FOR TEST SITES.

Ozh' Auto Moderate Comments vs No Login