If this happened, please go ahead and send us the samples! Generally, we ask that people wait four hours between swabs because waiting gives your cheeks time to recover and allows us to have a good backup sample in case the first one does not yield results. However, most people are able to get a good quality swab regardless of whether or not they waited the four hours. If we are unable to get a clear result from the samples provided, we will send you replacement swabs.