You can have as many Stryds as you want with one account.
This article does NOT pertain to Stryd Duo. This article can be useful if you have one older Stryd hardware and one newer Stryd hardware. NOT two identical Duo compatible devices.
Note the following:
1. Your Garmin watch can pair with many Stryds and will automatically connect to the right device when you go for a run. If you mix Stryds, leave the ANT+ ID set to 0 in the settings of the Stryd data field so that it can display power from both devices.
2. If you use a Polar or Suunto, you will need to pair with your Stryd each time you switch devices.
3. The Stryd app can pair and connect with both Stryd, but only to one at a time (Unless you have created a Stryd Duo). So, you may need to unpair and repair if you want to change your weight or update the firmware. Note that height, weight, and time will be set each time you connect to a device.
4. Regardless of how many Stryds you own, all data can end up in the same account. You can see all your runs in PowerCenter and/or the Stryd app on your phone.
Note that later on, you cannot distinguish which Stryd the data originated from.