Filtering or managing unused Previews in order to reduce size of C1 Catalogue

I have a C1 Catalogue of approximately 200,000 images and the majority of them have been taken on Full Frame Cameras. As a result my C1 Catalogue is approximately 620GB which means I have to keep this catalogue on an external SSD. The size of the Catalogue can be attributed to the Previews. As a result, I would like to have the ability to either filter and remove Previews from older images, or have C1 automatically do this in the case where images haven't been viewed/edited in the past 30/60 days. I think this would dramatically reduce the size of the C1 catalogue and allow me to keep the Catalogue on my much faster internal SSD.