There's no obligation for manufactures to keep every part available for 20 years.
My experience with my 1998 Chevy that's been my daily driver for the last 16 years ...
There's only been one part that I needed and couldn't get. It was the driver's side seat tilt lever. They ran out, quit making them, and they aren't available anywhere. Fortunately I was able to get a seat back adjustment lever for the passenger side that does the job. I had to wipe the incorrect markings off with lacquer thinner but no big deal.
I also found that GM no longer has seat cushions available. Other than those things there's hasn't been anything that I haven't been able to find and I've replaced A LOT of parts on my truck.
