Do lens implants last forever?

Lens implant life. They are made of plastics (acrylic, silicone, and pmma) that will last longer than us. The lens capsule behind the lens often opacifies a year or two after surgery. This is treatable with a yag laser in the office or asc. The lenses rarely migrate or develop any changes that would require replacement.
Yes. The implants are made of material which does not elicit an inflammatory reaction and is not attacked by the immune system. They will last longer than you will. That is not to say other problems can occur in the eye, such as macular degeneration or glaucoma, for example, which can effect the vision.