Leather is skin. It behaves like skin. It dries out, it takes colour from what it touches, and it improves with attention.
Everyday
Wipe with a soft dry cloth. Don’t put leather away wet, and don’t dry it near a heater. Heat is what cracks leather, not water.
Two or three times a year
Feed it with a neutral leather balm. Work a small amount in with your fingers, leave it an hour, buff it off. More often if you wear them hard or live somewhere dry.
What will happen
Pale hides darken. Edges shine where they rub. The footbed takes the shape of your foot and keeps it. None of this is damage. It is the reason to buy full-grain leather rather than something coated to stay identical forever.