Task extended table Active flag state management

Hi Team,

I have a custom table extended from task. Ideally after the action is completed the state has to be set as 'Passed'. I am confused about the active flag management here. 

Bcoz I have a job to check if this was passed 6 months ago I need to set the state as 'Expired'. So the question here is whats the best way to maintain active flag. Is it better to keep it active as true till its Expired or make it false when the action is done and the state as Passed.

If its active false is it okay to edit the states of tasks later on? I am of that thought if a task is closed no further update must happen possibly except worknotes maybe.

Any feedback here would be appreciated.

Thanks