I just completed a 1hr cycle (along the blustery Blackpool coast just ahead of Storm Caroline) followed by an easy 30 mins on the treadmill and a total elapsed time since I took Apple Watch off the charger of around 2hrs and I still had 98% battery.
I had my iPhone X with me the whole time which helps with battery life on the watch since it can provide the GPS.
But even if we said the majority of the battery life was used in the cycle we are still looking at only 2% an hour which means being able to use it for the entire IronMan without any “creative charging” on the bike, and possibly much more than that; and a significant improvement over my previous tests.
Of course Apple could have adjusted the curve at which battery use is displayed so it goes down more at the end end of its life, and in the actual IronMan I won’t have my IPhone as it’s not allowed, but it’s interesting and promising none the less.
More investigations to come., but would be interested in hearing others experiences in the comments too.