This. For HTTP 1.1 clients, Cache-Control already overrides anything set in Expires (a header dating to HTTP 1.0), so losing some precision on an approximate gu

This. For HTTP 1.1 clients, Cache-Control already overrides anything set in Expires (a header dating to HTTP 1.0), so losing some precision on an approximate guess far into the future that's bound to be ignored by most clients should be a sensible trade-off.