Going by my own car that I bought new in 2008 and still drive, the chemical residue on my inner windshield has been rather consistent throughout the time I've had it, so it is still off-gassing after all this time.

There are many unhealthy chemicals in just about every part of the car, and heat cycles keep releasing more of them. The source for the above infographic say many studies have been done, but many sounded like they conflict with each other and many seemed to focus on short term health effects.