The exemption allows you to remain in the country during a period no longer than 90 days. If you are staying longer, you must file a visa application. This means that migration control agencies could check your passport to see if, 180 days before you trip, you have a longer stay than 90 days. 180 days amount to a period of between 5 and 6 months. Check all scopes of the exemption.
You may start travelling at will as from December 3, 2015, as long as you have an electronic passport with at least there months of validity.