Nah, once you've got 8MM in the bank there's no point worrying about maximizing returns. You've already won. Keep it simple, pay off the house, enjoy life.
Add in a lump sum for the monthly utilities for a decade and make a house account. Have the house account pay all these other incidentals from that account which you otherwise ignore.
Then, anytime you look at your bank account, the future costs of living in that home are never reflected in the balance you see in your daily account(s)