Hi,
regarding an actual topic in Germany about publication of the timetable-data of Deutsche Bahn (German national railway company) and their willingness of a discussion with other Open-Data-Supporters it may be a good idea of providing an expiration dates for Wikidata-records.
In their open letter to Mr. Kreil [1] they announced that it may cause problems providing the timetable-data in an open way if e.g. anybody uses old data.
Marco
[1] http://www.db-vertrieb.com/db_vertrieb/view/service/open_plan_b.shtml