LDA shall be at least the Actual Landing Distance multiplied by 1.67.
Please don't read "actual landing distance" to be the distance you will achieve in a maximum effort landing. The actual landing distance cited is that used for the AFM by agreement between the OEM and Authority.
The average line pilot has very little chance of achieving that distance on the line. A better approach is to become VERY nervous as the actual available landing distance reduces progressively below the normal AFM required figures in an emergency/abnormal situation... and conduct your management assessments accordingly.