Polyurethane foam's lifespan is determined by several factors, including the type of foam, the quality of the installation, and the conditions under which it is used. Rigid polyurethane foam insulation, in general, can last for decades or even centuries, whereas flexible foam used for cushions or bedding may need to be replaced more frequently due to wear and tear. Polyurethane foam's lifespan can be extended by proper installation and maintenance.