The shortest answer: premium PPF lasts 8 to 12 years when properly installed and maintained. Eternal Shields PPF is rated for 10 years against yellowing, delamination, cracking and bubbling, the four failure modes that define the end of life for any film.
What affects lifespan in the real world? UV exposure is the biggest factor, cars stored outdoors in high-sun climates will see slightly faster wear than garaged vehicles. Improper cleaning is the second biggest factor and accounts for most early failures we see in claims.
The maintenance routine is simple: regular gentle washing, avoid automatic brush washes, and use pH-neutral soaps. Followed correctly, your PPF will outlast most other components on the car.