Breast implants are not lifetime devices, all the models and manufacturers have a limited lifetime expectancy of breast implants, sooner or later they'll break and require renewal.
Prior to full blown formal rupture the implants are invaded and calcified, literally calcium carbonate or gypsum is deposited at the scar shell or capsule around the implants, on the surface of the implants themselves or even inside the implant after tissue penetration into them.
This calcified reaction with aging breast implants is very beneficial and a good sign of protection against migration of leaked silicone, although might be painful due to the hard or solid touch it acquired. It takes years for the formation of such layer of gypsum, and once is built up the implant can be awaiting renewal years too.