It's been 8-10 years but when I was serving tracking pixels we were astonished how long we still got requests from residential IPs for whole hostnames we had de

It's been 8-10 years but when I was serving tracking pixels we were astonished how long we still got requests from residential IPs for whole hostnames we had deprecated. That means I would not trust DNS caching anyway. I'm not talking days here, but months, with a TTL set to mere days.