The TMO CellSpot is GREAT. I got it to boost my WiFi Calling but it's just a really great router. It has replaced the AirPort Extreme I had, which was failing anyway. But basically, I just made my CellSpot my main WiFi Router and best of all it was "free." It has incredible range.
Also, if you're at home with WiFi, go into Airplane mode w/ WiFi on and see if that improves your battery. I do that at the office where the LTE signal isn't very good and it extends my battery.
The CellSpot is really just the ASUS TM-AC1900 modified to prioritize WiFi Calling so it does use WiFi calling rather than boosting an LTE signal. It is faster and has much farther range than my old AirPort Extreme. I highly recommend getting one.