I can only endorse this, but would like to add that I always put my name and email address and a version number on top of the document. The additional version number is useful for keeping track of changes. Often I indicate what changed since the last version of the documentation or I have a separate HISTORY.txt file in the documentation folder including all versions, dates an a brief comment, what has changed.

If a question comes up later, I can first ask the questioner which date or version of the documentation they are relying on. More than once, the problem has been solved simply by sending the person the current documentation again.