It occurred to me that Tom Nakamura wrote in gmane.os.netbsd.help:
> meaning its safe for people with slower machines  (who doesn't want to
> build big packages ourselves) to install binary packages from
> /pub/NetBSD/packages/pkgsrc-2005Q1/NetBSD-2.0/i386 without worrying
> about conflicts/etc.

AFAIK yes, with the added remark that packages might get removed in case
of security issues. (If package foo was at version 1.2 when 2005Q1 was
branched, and when it was later discovered that foo-1.2 has a security
leak (fixed in foo-1.2nb3 in HEAD), foo-1.2.tar.gz gets deleted, but no
foo-1.2nb3 will be generated for 2005Q1. At least, that's my understanding of
it all.)