Definitely keep working on originals. Street gets on me all the time for posting covers. While in the 13 years of recording I have quit a few originals, I enjoy recording covers too. If you son is recording on his own (home studio), covers are a great way to learn on. Listen to the original and dissect every instrument you hear. Figure out how the artist came up with particular sound via experimenting with compression, eq, limiting, sidechain processing, panning, automation,.. the list goes on. Sound on Sound magazine is a good magazine and has many "how it was done" articles. I know personally If I hear a song be it new or a classic, I pick out every instrument in the mix. This is a blessing and a curse some times. The curse being sometimes its hard to just enjoy the mix as a whole.