I always sit by a window when flying to Europe (on the port side) so that I can see the aurora over the Atlantic as it is there almost every time if you look (although very dim at times).

Several times I've had my window fully dimmed and locked out. Sometimes they will unlock it for me on a promise to fully dim it before the sun rises, which is reasonable. Other times they tell me it is company policy to leave the windows fully dimmed and locked until breakfast, which I find ridiculous.