Stop using low DNS TTLs
The irony of all of this is that those TTLs are almost meaningless as a server operator anyway.  Even if you set your TTL to 5 minutes, there are a whole lot of clients that will ignore it.When I made a DNS switch at reddit, even with a 5 minute TTL, it still took an hour for 80% of the traffic to shift.  After a week, only 95% had shifted.  After two weeks we still had 1% of traffic going to the old IP.And after a month there was still some traffic at the old endpoint.  At some point I just shut off the old endpoint with active traffic (mostly scrapers with hard coded IPs at that point as far as I could tell).One of my friends who ran an ISP in Alaska told me that they would ignore all TTLs and set them all to 7 days because they didn't have enough bandwidth to make all the DNS queries to the lower 48.So yeah, set your TTL to 40 hours.  It won't matter anyway.  In an emergency, you'll need something other than DNS to rapidly shift your traffic (like a routed IP where you can change the router configs).