Having breast implants will not make you unaffected by gravity. The normal ageing process will occur and you may notice that your breasts may begin to droop. This is not usually a direct result of having breast implants but more just your natural ageing process.
Wearing supportive bras and taking great care of your skin will help to lessen the risk of sagging or drooping. Your surgeon will discuss your risks of implant sagging and they may suggest a combined surgical procedure of a breast lift with implants if they feel your skin is more prone to sagging. A breast lift will help to retain the results of a breast augmentation in spite of the natural changes to the body over time.