If you are lazy you can just put your money into one of the 10+ Vanguard Target Retirement funds [1] which are just varying mixes of their stock/bond funds + automatic rebalancing. It goes from 90%/10% stock/bond mix (VTTSX) at the high end to 30%/70% at the low end (VTINX).

1: https://investor.vanguard.com/mutual-funds/target-retirement...