Stryd can work great during ultra events that take many hours. The battery of Stryd can last over 24 hours and will continue to pass data to a watch or phone during that time. Typically, you will need to use a watch to keep Stryd in run mode (as most people walk long sections). The Stryd platform does accept very long runs over 8 hours but there can be some limitations.
1. The file recorded by the watch may simply be too large to display in PowerCenter.
2. It may take a very long time to load the data.
If you cannot see your run, you should try uploading data from Stryd with your phone (offline sync). Since Stryd does not record GPS or HR data, the file is smaller and can be displayed, even for very long distances.
The development team is aware of this limitation and is considering to address this in a future release. The workaround is to analyze your data in Garmin Connect, TrainingPeaks or other platforms.
If you have additional questions, contact firstname.lastname@example.org.