<p>The actual traffic rate to the site is irrelevant.</p>
<p>All of those settings (except for “default TTL”) only affect how frequently your domain’s secondary DNS servers poll the primary DNS server for updates.</p>
<p>If your zone only changes infrequently (which I believe yours does) then your value for “refresh” is currently a bit on the low side. Typically the primary should send a <code>NOTIFY</code> message to each of the secondaries whenever there’s an update at which point the secondaries grab the zone file immediately. These days the “refresh / retry / expire” mechanism is only a backstop to that.</p>
<p>In any event, it’s likely that your DNS provider is automatically syncing changes to all of the relevant DNS servers on the fly without using DNS’s built-in synchronisation mechanisms so the actual values are probably irrelevant.</p>
<p>Note that the “default TTL” field no longer means what it says. The real default TTL is set (in BIND at least) with the <code>$TTL</code> directive, and that’s only used when there isn’t an explicit TTL set on each record.</p>
<p>The “default TTL” field’s meaning was changed in <a href="https://www.rfc-editor.org/rfc/rfc2308">RFC 2308</a> and it’s actually a hint for <em>negative caching</em>. If your server returns a negative response (e.g. <code>NXDOMAIN</code> or <code>NODATA</code>) it’s how long the remote server should wait before trying again.</p>
<p>The current value is a bit on the low side, but there’s no harm leaving it as is. It’s often ignored anyway.</p>
