Well yes it's common to return both, but the HSTS header explicitly has a max-age parameter so the browser is bound by the spec to enforce TLS connections until

Well yes it's common to return both, but the HSTS header explicitly has a max-age parameter so the browser is bound by the spec to enforce TLS connections until the max-age is reached. So when you say browsers would "require HTTPS for all of eternity" my assumption was that you didn't like the 301 caching.