If you can OLCI successfully, I'd suggest that 4 hours is quite excessive. If you can't and need to see an agent (for anything other than bag tag printing and bag drop) then I'd suggest 4 hours just to be safe. Otherwise, 3 is more than enough. The choke point is the passport control. The airport isn't a zoo at that hour, and unfortunately, the PDI booths are staffed woefully accordingly. Class and status matter not.