I have checked the user guide for this application and there was no limit related to how much you can record except the hard disk space. If you can't record more than 4 days, then it means you don't have a bigger hard disk to store the recording. When the free space is consumed, the recording will stop. Based on the free space, you are able to record up to 4 days straight. Replace the hard disk on the NVR device and then you should be able to record more.