Customer-facing DNS should have TTLs on the order of 15 to 30 minutes. Halving those values to estimate TTL value to the end user, you get 7 to 15 minutes of ca

Customer-facing DNS should have TTLs on the order of 15 to 30 minutes. Halving those values to estimate TTL value to the end user, you get 7 to 15 minutes of cached DNS. That's about right for most user interactions on the web. Much longer and you run into all the trouble that operators have with keeping DNS accurate. DNS is hard. It is easy to break. And 15 to 30 minutes of waiting is about as much normal human attention span you can apply to a problem that sounds like, "Ok, we're all done, is DNS ok?" 5 to 10 minute TTLs only benefit operators. Certainly, any TTL less than 5 minutes is an indicator that your operators have no faith whatsoever in their ability to manage DNS.