Ive run a major CDN and authoritative nameservice. Its small enough to not matter in most cases. A quick swag is Id expect 95% of traffic to respect the ttl. An

Ive run a major CDN and authoritative nameservice. Its small enough to not matter in most cases. A quick swag is Id expect 95% of traffic to respect the ttl. Another 4% will appear to have some sort of minimum ttl on the order of single digit minutes. The last 1% transitions over the next hours. There will be a super long tail with measurable, but insignificant, traffic using the previous RDATA effectively forever. Im sure someone from DNS OARC has more recent and well quantified numbers.