The term 'perky' irritates me. I don't think it's a compliment. In erotica the term is inevitably applied to smaller breasts as if to indicate that even though they may not be gigantic they still have charm of some indefinable sort. It's become a cliche.
Nipple angle and posture are what contributes to the accepted look of a breast,and these can be influenced by diligent massage and underlying muscle development. Listen to dolfette about geriatric sag-- it is a matter of attention to support, both with proper brassiere and exercise. The purpose of brassieres is to haul the nipples upward afaik, in order to makes the figure conform to some ideal.