These "extended" check-in times really hack me off, because you may well find that at 4 hours before the flight the desk is not even open yet ! Or it may be the time that the desk first opens but it gives the impression that it is a minimum. If they're just doing one desk for an A330 it will take them a couple of hours to process everybody.
So what happens is that people just ignore the time given and make their own sensible decisions. In truth processing times at airports seem little different to before 9/11. Sure there can occasionally be long queues for security checks (that used to happen before 9/11 too) but not to this extent.
I would aim for 60 minutes minimum, and allow a bit more, although if seats are allocated at check-in the best ones may be gone by then. What's your departure point ?