A:Answer I have the same question. Not easy to find that answer. One place indicated that an 8GB card would hold 360 minutes (6 hours) so by calculation 128GB card would hold 96 hours, or 4 days.
The first problem to answer though is how to get the system to accept the 128GB card. I tried one and it would not work. However, I checked that card on our computer and it worked just fine, so it appears that the Defender monitor failed to recognize the card for some reason. From reading on the internet other people have had this problem as well. Still working on how to solve this problem.