Only keep a specific amount of images from ffmpeg image2 output?

Here is my ffmpeg command:

ffmpeg -rtsp_transport tcp -i rtsp://184.72.239.149/vod/mp4:BigBuckBunny_175k.mov -f image2 -vf fps=1/3 -strftime 1 $DIR/%Y-%m-%d_%H-%M-%S.jpg

That will out put an image every 3 seconds. I only want to keep the last minute of images (20 images)

If I was outputing to hls I could use the -hls_flags delete_segments to purge the oldest segments once the 20 file limit was hit.

Is there a way to do this with my initial command above?