Well assure them that they remain fabulous at 40 and beyond!:

I love this design - sassy and confidant - the way everyone should feel at this momentous benchmark! (I hope the designer will do a similar one for those hitting 50!)
You can make it a whole theme present by pairing the card with any of the following items with the same design:

Okay I know - T-shirts with writing can be hard to pull off after a certain age. But you can get this design on different styles of shirt - I particularly like this fitted style. Remember this is a for fun gift after all! ; - )

And put it all in the bag!

A gift bag that can be used later! How good is that! ;-)
(A note of full disclosure - I am a Zazzle Associate. Sadly, this is not my design! But I will get a couple of pennys if you link through from here and decide to buy - just so you know!)