evolution has probably been discussed on okp in the past,
but I still want to point out how this is applicable to
so many artists. Black Thought/The Roots being the most visible.

I can't remember a year where I didn't see any tourdates for Little Brother /Phonte/Foreign Exchange...and you can hear the progress in Phonte's performance..
Dude is nearing his 40's and in peak condition when it comes to MC-ing...

And like someone else said in this thread, So Help Me God is a rap clinic.