What would you do with $15,000,000?
This would go with any large amount of monetary gain as well. I would invest the 15 million in good growth stock mutual funds and live every year off of the earnings (10 v;erage) which would be 1.5 million per year(average). This would leave the original sum there (total would fluctuate) over my life and continue to produce an income for generations of my family as long as they let the original amount of money remain.
This is the same way to find out how much you need before you can retire. If you live now on 100,000 per year, you need to save 1,000,000 to produce that after you retire.
Make your money work for you,let this 15 million be a slave for you and produce you millions more over your life and live it up.
Richest man in Babylon (en.wikipedia.org)