Having my Note 3 for a few years now, I thought it only prudent to consider having a spare battery...especially with the Apple iPhone fiasco about slowing down operating speeds.
Yes, my present battery seems to be working just fine after all these years.
And, since I'm not in the frame of mind to buy another $900. smartphone (is my wife listening), the NEW backup battery seemed to be a good idea...especially for only $24.99.
(note: I think that there is also a less expensive refurbished battery)
To replace the battery on a Note 3, you simply have to 'pop off' the back cover.
Although a plastic tool could be used for the cover removal, you finger nail works just fine.
The battery is right there....no fancy clips to remove, no tape, no crazy connections.
Just replace...and go.
It takes a couple of minutes...if you're slow ;-)
As mentioned, a backup battery is always a good idea, especially if your usage is 'heavy' or your device is getting older.
Combine that with the inexpensive replacement cost here at IFIXIT, and this decision is a 'no brainer'.
Certainly consider the option!