The TCP/IP stack is not running long enough to provide an adequate cache, especially based on your assumption that an Amiga doesn't stay booted long enough to viably host a nameserver.
There are about two dozen users using my nameserver. I don't honestly know how many Time Warner Business Class customers I share a nameserver with, or what else their server does, but I have actually measured the difference between using their server and mein, and mine is on average about four times faster. Granted, that was five years ago, but I doubt it's changed much.
And, mine never goes down. Theirs does occasionally.