Ok I watch till 50% battery, I stop, but things happen so I am out for many more hours, that time still takes up battery even if you are not actively using it.

I stopped before dead battery, but I could not predict the future that it would be longer.

Lets take a look at 3 Sundays ago what happened to me. I went to church, my battery was at 60% after church I get out to my car and find a 4in slash in my car tire., I had to get my car towed to a tire place, had to get all 4 tires replaced (long story on why all for instead of just 1 or 2) and since my church is a good distance from where I live, I could not just simple go home as they worked. so Church, plus time to change the tire, when I got back into my car the phone battery was dead.

Why so low on the battery, well my dad when he drove my car broke my charger, so no charging in the car that day,

Things happen, you can not predict the future, so best save the phone battery and not use it on videos or Facebook or other things.