You ask: "Are we ever too old to care how we look?"
I think, 'no.'
But, our ideas constituting the 'care how we look' can change with age and/or life circumstances.

Being clean is caring about ourselves.
Being groomed is caring about ourselves.
Now, this is just my opinion, but fashion wear, hairstyles, nailpolish, bling, etc. is add-on, not necessarily necessary.
I know several older women of beauty and style. One of them wears no makeup, doesn't color her hair, wears no jewelry, and has a low budget wardrobe... but, she shines beautifully for everyone that knows her.