Do not toss the drawer phone -- give it a job
A phone with no SIM card is not useless -- it is just missing a phone number. Over Wi-Fi it can do almost everything it used to, so before recycling or trading it in, it is worth deciding whether it could earn its keep as a camera, a music player, or a backup device first.
Battery care matters if you plan to store it
A phone left plugged in and fully charged for months, or left to drain to zero and sit that way, both stress the battery over time. If you are storing it rather than using it daily, charging it to roughly half and checking on it every few months keeps the battery healthier for whenever you pick it back up.
Frequently Asked Questions
Can I still make an emergency call without a SIM card?
In many countries and on many devices, emergency numbers (such as 911 in the US, 112 in much of Europe, or your local equivalent) can still be dialed even without an active SIM, but this is not guaranteed everywhere. In an actual emergency, use a phone with an active SIM whenever one is available.
Can I use a messaging app like WhatsApp on a spare phone with no SIM?
Usually yes over Wi-Fi, but the initial sign-up typically needs a phone number that can receive a one-time verification code, even if you do not use that number afterward. Some apps also support linking a second device to an existing account -- check the specific app's settings for a "linked devices" or similar option instead of assuming it only works on one phone.