A key set rarely fails all at once. It fails one copy at a time, usually the copy that has lived in a coat pocket, a purse, or a neighbor's kitchen drawer for years. The moment you most need a key is the moment a worn copy turns out to be the one you grabbed. Sort the set now, while nothing is urgent.

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Find the original

Gather every key that opens your father's front door, side door, and any room with a lock, plus every copy anyone else holds. Set the originals apart and tag each one with what it opens. Copies made from copies drift from the original cut, so a key that turned fine at the shop can bind in a cold lock after a while. Keep the originals in one place that is not on the car ring or the house ring you carry every day.

Retire the copies that are going

Test each copy by turning it slowly in the lock, first with the door open and then closed. A key that needs a wiggle, catches at the same point every time, or leaves the bolt half thrown is on its way out. Do not wait for it to snap off in the lock, which is the worst place for it to fail. Pull the failing copies from circulation, and write down how many working copies remain so anyone who opens the envelope can see the count.

Name who holds the set

A set is only maintained when one person owns the list. Write a short card: who holds an original, who holds a copy, which neighbor or caregiver has access, and who orders the replacement when a copy wears. Keep the card with the originals. When a copy comes back worn, the card tells you who to ask for it and who needs the new one. That is the part of a key plan that keeps working when nobody is in a hurry.

Test on a schedule

Put a test on every visit. Try each working copy once from outside and once from inside, and note any key that feels rough or that you had to force. A lock that gets harder to turn needs a look from a licensed locksmith, not a fix from whatever spray is on the shelf. Ask the locksmith which lubricant suits that lock before anything goes inside it. If a key you need goes missing, do not drill or force the door yourself. Call a locksmith you have already checked, and keep the receipt with the card.

The next move

This week, collect every key that opens your father's doors, tag the originals, pull the copies that fail the turn test, and write the holder card. Then go to his door, try each working copy once from outside, and leave the card with the originals.