Geo failover: Adjust DNS TTL guidance

doc/administration/geo/disaster_recovery/index.md

@@ -67,7 +67,7 @@ must disable the **primary** site.
   - Physically disconnect a machine.
 
   If you plan to [update the primary domain DNS record](#step-4-optional-updating-the-primary-domain-dns-record),
-  you may wish to lower the TTL now to speed up propagation.
+  you may wish to maintain a low TTL to ensure fast propagation of DNS changes.
 
 ### Step 3. Promoting a **secondary** site
 

doc/administration/geo/disaster_recovery/planned_failover.md

@@ -90,6 +90,11 @@ gitlab-ctl promotion-preflight-checks
 
 Each step is described in more detail below.
 
+### DNS TTL
+
+If you plan to [update the primary domain DNS record](index.md#step-4-optional-updating-the-primary-domain-dns-record),
+you may wish to maintain a low TTL to ensure fast propagation of DNS changes.
+
 ### Object storage
 
 If you have a large GitLab installation or cannot tolerate downtime, consider