Apologies if you already know this, but there is a search bar at the top of the watch app on the iPhone that is a great tool for quickly finding settings. (scroll the screen up to the top if you don't see it); this is how I use it. In her first post in this thread, Night Spring told you that the duration can be set to 15 or 70 seconds. She didn't initially mention the name of the setting, but a quick search for "70" (as in 70 seconds) takes you right to Wake Duration. So much faster and easier than poking through the menus looking for it.