The key is:
Use an AutoText field rather than inserting the AutoText.
Update the fields when needed.

Consider storing the AutoText in a Global Template so that it is available to all of your documents rather than just those based on the template.

You can have a macro in your document templates, if you want, that updates all AutoText fields every time a document based on the template is opened. Note, though, that this updating will not work when the document is on a system that does not have the global or document template.