Interesting, so it does in fact seem that your cameras were designed to record video directly to their built-in storage devices. I'd never heard of that before. Usually the built-in storage is only big enough to hold the firmware and configuration, and not much else.
The message about your eMMC having consumed 95% of its life is a warning, not an error. It doesn't mean something is wrong. It only means that something likely will go wrong if you turn off eMMC protection and allow the camera to record snapshots and video to the eMMC device.
If you want the camera to be able to record internally, then put in an SD card and configure the camera to record to the SD card. If you only care about recording to an NVR, then you don't need an SD card.