Hi,
Thanks for using our plugins. I can help out here.
For the most part we do not do anything with past events. Unless it is a recurring event and we have a clean up system to delete those events after a certain time period.
Otherwise past events are there in the system and you could go back in and modify the content as you would like.
As for Google it would correctly read the structured data and know it is a past event, but beyond that we do not do anything else.
Let me know if you have any follow up questions.
Thanks