Due to the design of the heads, it is impossible to get a good look inside the valve cover through the oil cap but during my last oil change I ran my finger as best as I could inside the cover and came out with some hard black deposits. This is not a sledge, but small black chunks, carbon?

Now I am worried this will shorten my engine life!
Is this a common problem?
How do you clean it out of the engine?
How do I prevent this?

You can try auto-rx.com. People swear by this stuff.

Best way to prevent it is frequent oil changes.
I've got vehicles with 100's of thousands of miles on them and NO sludge.
I change the oil and filter every 300 mi.