I've used their stuff for years, from cables, to powerbanks, to wall adapters. They last and they are dependable.

Biggest thing to take into account (as others have mentioned) is to turn of as much on your phone as possible to keep it from using too much power. Even reducing the screen shutoff to 5 seconds can make a massive difference in battery life.

Also, be aware that cold weather adversely affects battery performance. If temperatures are around freezing where you will be, you could see a reduction of 30% or more in effectiveness.