All breasts relax as time goes by. This is because:
- the weight stretches the skin
- elasticity is lost with age
- the amount of breast tissue often decreases as the person gets older.
These three factors mean that breasts can be expected to relax and sag whether or not there are implants present.
The implants add some weight to the breast, which may increase the rate of relaxation, and yet implants and surrounding scar tissue can provide some internal support for the breasts.
The overall result is that usually the breasts sag less - more so if you wear a properly fitting bra regularly.