I do a lot of JFK-TLV (23:35 round trip), and I prefer to do two shorter breaks, rather than one long one. I've tried several different ways of doing the breaks, and think that two different sized breaks work best for me. (I have yet to insist that we do it my way, though. I always go with the what the crew consensus is--as do most guys, I think).

First of all, it's torture to sit in the cockpit for that extended period of time, especially on the back side of the clock. You're tired, but don't want to drink coffee, because you're afraid of messing up your break.

To take a long break is great--if you actually get some sleep. I've had legs where I only managed to sleep for an hour or two of my 5:30 break; that sucks. Two breaks gives me another chance to get some sleep, if conditions weren't right for a good nap on the first break.

BTW, I've found that it's a good idea to keep the door to the bunk room open between shifts; this allows the room to cool off a little. I've seen a 5 degree temperature drop by doing this.