I am almost certain check-in opens 2 hours before, though note the use of the word almost. People do arrive very early there, and queue up in readiness. Personally I think it's probably better to arrive 90 minutes beforehand to get that queue out of the way. The point being that if you turn up 3 hours beforehand you won't be airside much sooner than the person arriving at 90 minutes. Security is reasonably swift, passport controls are the unknown, but it is vastly quicker than entry. And it is not as though le salon vaut le détour...