A person’s handwriting becomes precious the day they can’t write anymore. Keep the birthday cards.

Handwriting is one of the few things a person makes that nobody else can reproduce. It is less a message than a physical trace of one specific hand moving, which is why a shopping list in the wrong drawer can stop somebody cold years later. None of that value shows while the person is still around to write more. It arrives all at once, later.

If you have cards or notes in a drawer, you might move them somewhere they will not get thrown out in a clear up. A shoebox is plenty. It costs five minutes now and cannot be done at all afterward.