Why it matters
TTL controls how long old DNS data sticks around. If a record has a TTL of 86400, some users may see the old answer for up to a day after you change it. Before a domain moves to a buyer's website or email service, lower the TTL a day ahead so the cutover is quick. Raise it again afterward. A common mistake is changing records at the moment of closing with a high TTL and then thinking the change failed. It is usually just cache. TTL affects DNS records only. It has nothing to do with the registration's expiration date.
Source: datatracker.ietf.org