It happens when women go under the knife for breast surgery you have to re-do it again, as breast implants are not a lifetime device.
That's not entirely true, you don't have to replace them if there's nothing wrong with them and you certainly don't have to do it every couple of years. She only had the last set done around 2 years ago.
"Breast implants will not last a lifetime. They are likely to need replacing at some point." Source: NHS (External Link/Members Only)
She still looks hot, but those orbs were fantastic!