Time horizon
The length of time before invested capital is needed.
The time horizon shapes how much risk and illiquidity a portfolio can sensibly carry. Longer horizons can bear more volatility and a larger allocation to private markets.
Horizon is a family's quiet advantage. The longer the money can stay invested, the more volatility and illiquidity it can sensibly carry, and the more it can lean into assets that reward patience. Misjudging the horizon, in either direction, is one of the more expensive planning errors.