Another couple of tips for battery life is turn off the WiFi and keep the camera warm until you're ready to shoot.
I normally run two cameras: a 3 and a 3+ (both Silver)
I carry 4 spare batteries and normally get about 40 mins out of each if they start out warm (at around 15*F)
Also, those little anti-fog strips are money. If you're going to change batteries in the cold, definitely include them in your kit. One is usually enough for several day's filming with regular battery changes.