Edward Lewis writes:
Unrelated, or just less correlated than you might otherwise imagine?
Unrelated.
I'd studied an event which made it apparent that resolvers vastly ignored the long TTLs in play. At the time I learned that two popular strains of resolver code had an "internal" limit on the TTL they would accept [which is old news now], meaning any authoritative server operator who was banking on long TTLs to lower traffic was not going to realize any benefit.
The "ignored the long TTLs" goes right to the heart of the question though. If you tell me something akin to "it looks like TTLs under six hours impact query refresh rate but then starts a rapid decline to where almost no TTLs are honored for longer than 24 hours" then I'd say that does not indicate TTLs and traffic are unrelated, just related in a smaller window than those favoring long TTLs would hope. Conditional correlation != unrelated.