Use Your Apple Watch to Test Beta Updates

Apple always recommends against using your primary devices to try beta software updates because you never know what might happen. Sometimes, the bugs are so nasty they might break your device, but that’s something you wouldn’t have to worry about if you use an old Apple Watch instead.
By keeping your old Apple Watch, you can try the beta updates months before they’re available to the public. And if the beta has a bug that hinders your battery life or performance, your new Apple Watch will still work perfectly for daily use.