Re: how long should i charge my new galaxy note 4 for the first time?
Actually it really does matter. Read The Care and Feeding of Lithium Polymer Batteries. Look at the conditioning section. Condition the battery. (Some people in the industry say that polymer batteries don't have to be conditioned. Some of us are more cautious. It doesn't hurt the battery to condition it, so condition it.)
Then (as long as you don't let it drop below 40% more than a couple of times) it doesn't matter.