Etsy sends out Renewal notices to their shopkeepers usually 2 weeks early. If you pay before the final due date you basically lose the overlapping time and they are double-dipping.
IE: if you get a notice on July 1st for renewals on July 15th and you pay on July 1st then your ads are renewed from the July 1st date and you just lost 2 weeks of time from your previous renewal.
Also never pay your fees to ETSY until the due date.