The decision
Copies are for failure, not for convenience.
Three cards is not three times the storage. It is one set of secrets and two answers to the question of what happens when one card is gone.
The arrangement you pick should assume something bad and boring: a lost wallet, a flooded flat, a card left in another country.
Whatever you choose, write it down in the handover note. A copy nobody can find is not a copy.
Three arrangements
Pick one and stick to it.
-
I
Carry, home, away
One with you, one at home, one somewhere else entirely. The default.
-
II
Home, home, trusted
Nothing carried. Two in the house in different places, one with a person you trust.
-
III
Mine, ours, theirs
One personal, one household, one held for whoever will have to look one day.
Decide once.
Write it down.