My '93 is now 8 years young, with 150,039 miles on it. The paint looks fabulous. Sure, there's some rock chips and the like.
My secret?
Meguiar's Paint Cleaner (also known as Clear Coat Body Scrub). This cleans EVERYTHING out of and on top of the paint. Strips it clean. It's a wipe-on, wipe-off kinda deal. After doing that to the entire car, then wax with Meguiar's Deep Crystal Carnuba Wax.
Pretty as a picture.
I do this at least 4x a year.
I have invested a small FORTUNE in finding out what works well for black cars, over the last 8 years. 2 of my 3 cars are black. The Meguiar's stuff works very, VERY well on all three cars (one is dark green, btw).
Yes, it grays up eventually. That is nothing but dirt and gunk on top of the paint. Washing won't get that out. Buffing it with a compound will only grind it back in there. But after doing the above-mentioned routine, it is practically brand new-looking, IMHO.
The car may 'look' clean, but I guarantee after using the paint cleaner, the towel you use to wipe off with will almost be black itself. Which is dirt you cannot see hiding in the paint.
You're never going to get the old bugs and parking lot dings out of it, but with some elbow grease, you CAN make Super Black look good. It just takes some work.
JMHO.