The veins in my hands have always been close to the surface, and tended to be prominent when they - and the rest of me are hot. Not much of a problem at 30 - but in your 70s when the skin on one's hand is thinning, they are immediately aging.
I envy DH and DD, their veins are hidden deep in their arms and never show However, DD was discharged from blood donating because they had such difficulty finding her veins and DH always comes back from the surgery after a blood test with an arm like a pin cushion, although they have recently employed a nurse who has the knack and when blood test time comes he makes sure she is the nurse he sees.