Legally they are required to sell the parts for 10 years.
After that they have no obligation but many times parts are still available.
If there is any demand for the parts the aftermarket will come through.
Without demand I'm confident that part can be obtained from a scrap car.
As an example of demand I have 2 projects. An 87 Ram and a 69 Super Bee.
Some parts for the Ram are almost impossible to find.
Any left are either someone's baby or their work truck. When they finally scrap them the truck is killed and it gets crushed right away.
The 69 I have no problem getting parts. Restoration places like Year One and many others like it make almost anything you want for these musclecars due to the demand.
I thought that 10 years was a federal regulation for automobile mechanical (not trim) parts. I read here that the fuel lines for a 97 Intrepid were no longer available through Dodge. If this is accurate, I suppose that to obtain parts on an older car it might be necessary to first obtain an attorney?