They never should have been sold as a "Good for ever" product.
They all have a design life.
Newer materials are developed and their subsequent use in breast forms,
result in a longer design life.
But it is finite.
Also, products can go wrong.
I've a friend who had
augmentation Mammaplasty six years ago. with PIP implants.
She is having them replaced next month as a precaution.
Story here
and here