Customer lists can be replaced as often as necessary (barring any contractual limitations). Currently, a new list must be uploaded by 6AM EST in order to receive same day results.
Please note that our service is not additive and we only monitor one file at a time. Therefore if you have new/more customers to add to your list you must upload a new comprehensive list, not just another file with the newest customers.
For example, if you have 75,000 customers on January 1st and by February 10th you have 10,000 more, the new file would need to have 85,000 records, not just the new 10,000.