GoPro battery in the cold?

So how do you folks manage to keep your GoPro batteries going and going while in cold weather environments? I recently dropped my GoPro Hero 4 off the summit of El Altar in Ecuador while popping it off my helmet to warm it in my jacket. Now looking to buy a new one, I see that the new models don’t have extended battery packs like the Hero 4 did. In the cold with the extended pack, I could get about 2 hours worth of life out of the camera. What strategy are you guys using to keep these new models running for more than an hour? 

Is the key to just buy 5 of them??   

I’ve had bad luck with Gopro batteries as well.  I used to do alright when I had the old Hero 1, especially with the added battery pack, but when I upgraded to the Hero 3 it was pretty bad (for snowboarding trips mostly while it was cold).  I bought some off brand extra batteries cheap off amazon and would keep them in a backpack or insulated pocket and just keep them warm.  Just got the Hero 5 and it lasted me a whole day on the slopes in 15 degree weather.  A lot more happy with that.  

I’ve seen off brand housings that claim to be insulated but when they’re exposed to cold weather (below 10 degrees or so) I doubt they make much difference.

Id recommend just buying a couple extra batteries. Usually the cheap ones on amazon work about as well as the ones gopro sells for $20 or more.  It’s a pain switching them out, especially if your hands are cold, but it’s doable.