Yes  is the unavoidable answer to that question. 

We'd love for your iPhone to have an infinite battery supply (and Apple is improving batteries all the time) but that is still a way off. 

However, there are a few things you can do to prevent your battery from dying quickly:
  • Keep it warm. If in an exposed pocket your battery will cool quickly and your phone may well shut down and restart again once the temperature improves. 
  • Have a booster. They're not cheap but they may well be a worthwhile investment - if you're phone can't do a few hours on the slopes it will probably struggle to do a day in the office as well. 
  • Quit other apps. Double tap your home button and swipe up on other apps to prevent them from using your battery in the background. 
  • Turn off Bluetooth and WiFi. Swipe up from the bottom of the screen and tap the icon - nice and easy.