Just about anything. We support a fully customizable TTL value from 60 seconds and on up. You’re not forced to select something from a drop-down menu with very limited flexibility. You can enter anything between 60 seconds and one year (in seconds, of course). Whatever meets your business needs.
Why do we not allow you to enter a TTL value lower than 60 seconds? To answer that simply, we’ve found over the years that many of the DNS resolvers operated by ISPs tend to ignore values lower than that. Customers who set the TTL to a low value generally want the flexibility to make changes quickly, and in our experience it seemed to make matters worse. We hope that 60 seconds is sufficient for your needs. It is the default setting for DNS Failover ‘A’ records and seems to work extremely well for our customers.