Disclaimer: I am 33, have >$100k in student loans (at about 3%) and >$450k in a mortgage (at 3.5%).
Assuming $650k after taxes, I would take 10% for a baller family vacation. I'd take another 10% and divide it between my parents, brothers, and in-laws. Would be about $10k for each "unit". I'd take another 10% to give to three charities that I already like to support. I'd put the remaining $455k in my brokerage account not to touch.
It wouldn't change my life in the sense that I'd still have to work, obviously. But it would relieve a lot of long-term financial pressures, and would probably set me up for an early retirement (at age ~50 or so), if that's what I wanted when I got to be that age.