Garmin-Kevin, I was pretty thrilled by the potential the stamina feature!
I'm not deceived even though Im not done testing it completely.
BUT !!!!
Today I used it in a marathon for the first time.
It was the first time I had the occasion to go over the stamina remaining distance(38K), well not quite because as I neared 38K ,the remaining distance started to stalled even slight increasing. When I finished the race, it was still showing 2K. My reasoning is that it may not be a bug but instead, just the fact that since it was the the biggest recent race I had run since buying the watch, this race sampling was showing the stamina algorithm that my capacity was greater then what it was seing within his horizon. I expect the stamina in incoming workouts are gonna be more precise. Makes sense?