@Tom *******
no I wouldn't waste the money on it if you're comin' back after the extension expires BUT what I would do (so that you don't have problems on the next ED visa) is go to the immigration office with a letter from your school stating you are stopping studying on the day you are flying out of the country so they can cancel your current extension.
That way you won't have any problems when you come back in and go to apply for a new ED visa and extension.