old? heuristic in refreshIsCachable()

What prompted the heuristic of not caching responses that expire in
under 60 seconds?

I ask because in rproxy scenarios, with surrogate-control headers, it's
quite common to give the surrogate (squid) a low expiry, to ensure
freshness to new visitors, while giving clients a high expiry, to reduce
surrogate load.

I'd like to remove this heuristic altogether, but there may be a useful
reason for it...

Rob

-- 
GPG key available at: <http://users.bigpond.net.au/robertc/keys.txt>.