Anyone in their mid-20s that wouldn't sign a contract for $24M is an idiot.
Eliminate all of the risk for the rest of your life and be set no matter what happens (within reason). Maybe you are leaving money in the table, but probably not much. If you become an underpaid superstar, well, you will most likely recoup a lot of it when you finally get to FA T age 30. If not, well, you are set for life and can even live pretty well, just not insanely well.
Yea, sign if offered. No real downside.