FarmCam Mobility records motion events in clips between 6 seconds and 5 minutes (if continuous movement).  A 16 GB SD card can save up to 1389 minutes of full HD quality recordings. If bitrate is lowered, the SD card can save significantly more video recordings. You can change the bitrate under Settings --> Display --> Quality --> Clear, 

64 GB SD card is the largest memory card to be used. It saves 5556 minutes of full HD quality recordings. 

When the SD card is full it automatically deletes the oldest recording.