it depends on what you want to do -- without context of what you are offering and what steps your subscribers are taking, it is difficult to answer
for those who have "completed" the automation/sequence already, is there a natural next step or a new phase that you can take your subscribers into?
what about using a questionaire to find out what they might need/want to get to the next level?
remember broadcast emails work too, those who have "completed" past actions will tend to be more likely to continue to stay engaged with your new broadcast emails
hope this helps,