An interesting thing to note is that Garmin, Coros, and Suunto are pretty much the only brands used by long distance runners, and all three companies have really optimized them for long battery life. I really love my Garmin Fenix 6, and the battery on it lasts around 10 days-2 weeks depending on how much running I record with it. It's funny how most people don't know about Coros or Suunto outside of the running community though.