One spare is never enough
A spare under the planter is the first place anyone looks, and the copy lent to a cousin during the last storm rarely makes it home. Most households need more keys than they have: one for each person who lives there, one for whoever checks on the place while you travel, and one kept somewhere sensible for the day the main ring goes missing at the terminal.
Copies are cut on site from your own key, for every outside door and the smaller locks around the property. Each one is turned in its lock before it changes hands, so nobody finds out at night that the new copy only opens the door halfway.
If you are not sure how many keys are out there, that is worth sorting before more copies are made. A rekey first, then copies for the people you choose, gives you a count you can trust.

