Decide what the spare is for. It might be a temporary replacement, an occasional camera or a device used for a specific application. The preparation differs: a phone kept only for photographs does not need the same active service arrangement as one expected to replace a lost everyday phone immediately.
Check whether the device still supports the applications and security updates required for its role. Use the maker's current support information rather than assuming that a phone which powers on remains suitable for every account or task.
Keep access recoverable
Make sure you know how to sign in legitimately when the device is needed. Keep account recovery information in an appropriate private place, not taped to the phone. Do not make the spare your only copy of a recovery code or an important file.
If mobile service is part of the plan, verify the carrier's current activation or transfer process for that model. A SIM-shaped slot or a past working connection does not settle what is needed today. Record the steps you would need to take without storing sensitive account details in an open note.
Store it according to the maker's guidance
Read the device's instructions for longer-term storage, battery care and acceptable conditions. Apple, for example, publishes battery guidance covering storage preparation and periodic attention. Apply the relevant guidance to the actual device rather than keeping every spare permanently attached to a charger.
Store the phone where it will not be crushed, exposed to unsuitable temperatures or lost among unidentified cables. Keep a known compatible charging lead with it if that makes the arrangement easier to use.
Choose a review interval that fits the intended role and the manufacturer's instructions. During a check, confirm that the phone starts, the necessary application works and the accessories remain in place. Perform supported updates as appropriate and note any limitation that affects its purpose.
When the device can no longer fulfil that role, reconsider keeping it. A spare that only creates false confidence is less useful than a clear plan for replacement or service. If you retire it, use the platform's official data-removal and account-removal process before recycling or handing it to someone else.
