Keep Your Old Apple Watch As a Backup
You never know what will happen in the future. You might break your new Apple Watch or just lose it somewhere. Whatever the reason, it might be a good idea to keep your old Apple Watch as a backup.
You just need to be sure you do it the right way. It’s recommended that you keep your Apple Watch battery at around 50%. Don’t fully charge it or discharge it.
After you turn your Apple Watch off, make sure to store it in a place that’s cool and doesn’t have any moisture. Apple recommends that the temperature is around 0º and 35º C (32º to 95º F).
Apple also recommends charging your Apple Watch to 50% every six months to ensure the battery remains in good health.