Nobody stood a 12-hour watch, ever. Four hours was about all a bridge watch could take holding binoculars up and looking at nothing. I wasn't on subs, but my department on our destroyer (radio) stood rotating 8-hour watches when at sea.
I use SH3 Commander and the 8-hour GWX model, with 3D Views set to 1024. I come out of TC every 4 hours and change all the watches, and then enjoy the view for awhile. Works great for me.
