I'm not in this position, I've thought a fair bit about it since it's in the realm of possibility. This is what I'd like to believe I would do:

Buy 30yr Treasury Bonds with enough of the cash to generate ~$200K/year passively for the next 30 years.

Then proceed to continue my normal life. I'd treat the extra income from the bonds like a raise, invest it smartly, buy things as I would normally. Except now I have an immense buffer to stop current work and/or the freedom to pursue other interests.

But I wouldn't change anything in the first year of such a cash influx.