I didn't understand the question.
Two parts
1 - can I make a second event that fires after a period of 180 days but with only say a 33% percentage of firing per offset to mimic the province being cored by the new government
2 - in EU III you can have events that make it so that a province will randomly defect to another country (usually if it's cored or a small colony near a large nation and you have bad stab)
Limith - I don't want them persistent really.