Here's my take. I haven't posted on here in a while. I fly the 757 and 767 and on long flights like the one you were just on, I try to take several things into consideration. If the flight is going to take place mostly at night(mainland U.S. to Europe) I turn the sign off at cruise if it is smooth. If we encounter or anticipate turbulence, I turn it back on. If all signs are pointing to smooth air for a few more hours after the 1st relight of the sign, I'll turn it off again. It it looks like we are going to be in and out of choppy air, I will leave it on, even if that means several hours of flying with it on. My reasoning, the modern aircraft have automatic announcements when the sign is turned on. I don't want to cycle it all night waking up the passengers who are trying to sleep. I discuss with the FA's that if we anticipate areas of real turbulence, we will give them a call and they will strictly enforce the sign. Otherwise, we have made announcements and if someone gets up and moves around with the sign on, it is at his/her own risk. We don't have too many nazi enforcers at my airline but if we are going to fly through areas of known turbulence, we will inform the FA's to enforce the sign. The last thing anyone of us wants is for a cabin crewmember or passenger to be hurt on our watch. At the same time, we want you to be comfortable and feel free to move around on long segments.

On a long day flight, we will try to keep the sign off as much as possible. What happens sometimes on long segments is multiple seat swaps in the cockpit with augmented crews going on breaks and forgetting to discuss the seatbelt sign with those returning from break etc. I will make an effort to give more thought and discuss seatbelt sign usage more often with the other pilots I fly with in the future.