Create a rule at the event of "Cron maintenance tasks are performed"? I created a rule to be fired when "Cron maintenance tasks are performed".

Now I need an action to check delete all nodes of the content type: "Question" that have the field "Delete" set to "yes" 

How can I do this?
you could use hook_cron_queue_info to create a task that sits in a queue and happens on a timer. This would account for the potentially long duration of the task you mention.