Regarding the photo library, I can speak for my wife. We have a kindergartener and one of my wife's favorite activities is to watch pictures / videos of our kid in bed. She can do this for hours on end to entertain herself.
She also likes to watch movies on an iphone instead of a big screen cause she can use it while performing other tasks (cooking, cleaning etc). She has always said no to a larger form factor like a iPad but I think this might be a good use case for her.
My wife also watches content on phone and iPad. Usually in a room with a TV in it. Doubt she's intentionally watched something on a TV screen for weeks. I mostly watch on a second or third screen while working.
Our TVs are used by the kids, and even then they will happily take an iPad instead.
She also likes to watch movies on an iphone instead of a big screen cause she can use it while performing other tasks (cooking, cleaning etc). She has always said no to a larger form factor like a iPad but I think this might be a good use case for her.