As the DTS-AMS flight flys with the prevailing wind, there actually may not be a need for a relief pilot and therefore crew rest. Seat 4B could be released at the last minute when the actual winds aloft are known, and the seat allocated for upgrades or last minute WBC ticket purchase.

If there actually is a pilot utilizing the crew rest seat adjacent to you, there will probably be more disturbance, when compared to a normal passenger. We have been on many flights and have observed many crews in crew rest seats, it is very very rare that they get into the seat and rest for the entire period. More often than not, they are getting in and out of the seat, to the galley to chat, or get their special crew meal. Having the crew rest seat at the aisle makes all this somewhat more convenient. They have most likely seen all the movies they wanted to see on the entertainment system, and are less likely to just rest or sleep than the average passenger. On the other hand, the seat is sometimes unoccupied for long stretches of time, so it really is a mixed bag.

While many crew members are considerate to passengers, I would personally choose an aisle seat on any long flight, and avoid sitting next to a crew member, unless I really wanted to talk to him/her.

Looking at advance seat assignments is usually a good indication of the desirability of the seat. The aisle seats are almost always selected first, before many of the window seats are taken. Frequent Business class travelers really do not have a strong urge to look out the window during the departure and landing, and they prize the convenience of being able to access the aisle without stepping over anyone. The passengers whom select the window seat are probably the ones that want to mostly rest, and broadcast their intention by their choice of seats.