How Accurate is the Garmin Stamina Feature

So I've been using the Garmin Epix 2 constantly since it came out. I think it's a fantastic sports/smartwatch. I know it's very expensive, but I think you can add great value. Importantly, although this was initially available only on the Epix 2 and Fenix 7 series, the stamina feature is now available on the Forerunner 955 and Edge 1040. Although these are all higher-end devices, it is a feature that is becoming more accessible at a lower price point and hopefully will continue to become more accessible in the future.
This was an important test for me as I had signed up to do a 300 km endurance ride in just over a month, and the stamina feature told me I could only cycle 216 km. With this in mind, both to test my fitness and the Garmin stamina feature, I wanted to put this to the test in a controlled environment. The most controlled environment I could think of was my home gym on my WattBike using Zwift. So that is what I did at 4 am on a Saturday, I started riding, and after nine hours, I confirmed that in my experience, the Garmin stamina feature is very accurate.
If you are interested in purchasing the Garmin Epix 2, please find the link below:
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If you are looking for an answer to the question of how accurate the Garmin Stamina feature is without necessarily putting it to the test yourself, I hope you find this video of use; if you have any thoughts or questions, please leave them in the comments.
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