They don't want it to last longer, that is one of the reasons they chose this specific biopolymer. The splint provides a structure for the airways to grow in/a

They don't want it to last longer, that is one of the reasons they chose this specific biopolymer. The splint provides a structure for the airways to grow in/around/within, making sure they don't collapse in the meantime. Once the airways are properly developed the splint is no longer required. From the article: "The material we used is a nice choice for this. It takes about two to three years for the trachea to remodel and grow into a healthy state, and that's about how long this material will take to dissolve into the body," says Hollister.