An estate planner must be knowledgeable about the substantive law of wills, trusts, property, tax, etc., but he or she must also have the vision to anticipate and provide for changes that might occur in the testator's or settlor's circumstances between the formulation of the plan and the final disposition of the property involved. These changes will be of two different types: one concerns the property that the client owns and hopes to pass on to her family and friends; the other concerns the intended donees themselves, the persons to whom the client intends to pass the property and whom she hopes to benefit by the disposition.
John H. Garvey, Drafting Wills and Trusts: Anticipating the Birth and Death of Possible Beneficiaries, 71 OR. L. REV. 47 (1992).