this should be done 1 week out. but for each event you need to identify the zip codes that you might be performing the best in or has the majority of competitors in it, and target them specifically to see what growth you can achieve in a particular area if you try. the key is while the sale is on to keep it advertising going on TV, radio, press. especially if it goes for 3 or more days and have the count down till the end of the sale to try and press the call to action.