The battery life on the Garmin 935 is everything it is hyped to be. I recently used mine for an adventure race of over 20 hours and it was still going strong. Size and performance have been great as well. Customer service cannot be beat. Highly recommended.
If I were a runner, this would be a must. I don't run anymore but great for swimming. HR function works fine wo a strap. Interface with Garmin Connect Outstanding for tracking activities.
Another outstanding Garmin product. Battery lasts about 3 wks.
I have had the Fenix 3hr, Forerunner 235, and Vivoactive Hr. This is simply the best watch I've used. Battery life is long and a lot of useful features and running metrics. Last year I biked a lot but this summer I've been mostly running ultras.