The milestone will be considered achieved when articles for all 1154 sites on the official UNESCO list have been created and linked in from the UNESCO World Heritage List page. However, the project will continue indefinitely, as new sites are added yearly (usually in June or July) and the articles of existing sites can always be improved.
Make sure every listing has at least one link to the appropriate Wikivoyage destination.
Once a country's listings are in order, tag it with a comment like this: <!-- All sites up to 2008 -->. Use last year the list was updated, not the current date.
This tag refers only to completeness (are all sites listed?), not whether the articles actually exist (red links).
As of March 2009 - please remove the relevant countries from the list once stubs for all sites in the country has been created, and sign your name with four tides ~~~~ if you intend to work on a country.