If the witnesses are unavailable, it can lead to delays and added expense for the heirs and the executor.
To anticipate the potential problems, “self-proving affidavits” are often used. They are statements signed by each of the witnesses under penalty of perjury, generally right after the Will is executed and witnessed, that the person making the Will did, in fact, sign it, appeared to be of sound mind, and was signing the Will freely. (In some states such statements must be signed before a notary public.) Your witnesses won’t have to testify as to your will’s validity when you die, for the affidavit speaks to the will’s validity and serves as extra insurance that they witnessed your signature. This “Self-Proving” Affidavit also avoids problems that may arise if the witnesses cannot be located.