The next run time is being set after the task is successfully finished. So, if the tasks takes 10 minutes to finish, the next run time will be 10 minutes later. Regrettably, right now it is not possible to determine whether the task will finish or not. There are already some attempts how to fix this in future versions. Right now, you can check it manually or, create another task that will be execute after your task and will re-set the next run time for this task.