There was a huge debate about battery chemistry, the workings of Lithium Ion technology, training batteries, and various other comments relating to battery performance. This needs to stop!
There are many factors to battery life in the first few days of usage.
1) User excitement. Let's face it, we all get excited when we get a shiny new toy and want to play with it a lot.
2) Sync. Everything needs to be synced. It may take longer than a few minutes to do so.
3) Updates. Often new devices have an OTA available upon opening or within a few days of the device release. Not to mention the apps contained in Android that need to be updated.
4) Android itself. Here's a big one. Android monitors everything. Including user habits. When a device is new, Android monitors your user habits. What apps do you like? What apps do you avoid? And it monitors the battery usage.
5) And other topics I haven't covered, but that's a different post.
This is where a lot of debate around a similar topic is and needs to be addressed by someone not involved in the debate. So here it is: Yes, it's a good idea to put your phone on the charger when you first get it, let it get a full charge, and leave it on the charger for awhile. Why? Not because of 'memory effect' or 'training the battery'. But because it forces the battery monitor software to acknowledge the phone is fully charged. Use the phone until it's down to 3% or turns off. Then a complete charge while the phone is on. I do this for every phone I get. It helps the battery monitoring code to get a fix on the full capacity of the battery. Because battery capacity will vary (in some small amount) from cell to cell.
Doing the charge from 0-100% while off does nothing for the battery monitoring software. So I always either connect the charger at 3% (Android is programmed to shut down at 3%) or, if it shuts off, I plug in the charger and force the unit to turn on manually.
So, in the end, if you're getting bad battery life and the phone is new, you factory reset it, or you just took an OTA, it's not abnormal. If it's after an OTA, do a factory reset and let Android settle in for a day. If it's still seems like the phone is still discharging faster than you think it should, then you should seek a replacement, as the device may be defective.
I hope this settles the battery dispute. If it doesn't, then I will likely lock this thread.