I am an online instructor. Students are informed on the first day all emails are returned within 24 hours. I post office hours and days I am available. As much as you would like to be available 24 hours, we as instructors have personal lives and in each new class, there is a student of group of students who feel I am not available when they need help because of the time difference, their own work schedules etc. Is it really possible to be readily available to every student?