As long as your feeding/your fish are pooping, it should keep on producing skimmate. Keep in mind though that some skimmers can be sensitive to changes in your water. For example, if I stick my arm in my tank, my skimmer will stop making skimmate for about 10 minutes. If its not producing, try adjusting it so that it does. I can set mine to produce a small amount of dry skimmate, or a lot of wet...
HTH