Auto Delete Video Previews

You can post feature suggestions on the adobe Premiere forum. 

https://community.adobe.com/t5/premiere-pro/ct-p/ct-premiere-pro?page=1&sort=latest_replies&filter=all&lang=all&tabid=ideas

But Allowing a program to automatically delete files could be dangerous.  and Gotta say it's crucial that you manually monitor free drive space on a regular basis.   Many programs can create cache files if you're not paying attention and people save files willy nilly to their desktop etc.  You should keep at least 20% free space on your startup drive and at least 10% on other drives...  (at least that's the accepted rule).    I remember tech tool pro (a paid mac utility - not cheap) allowed you to set up automatic warnings.  I imagine there are other alternatives...  When I'm called in to troubleshoot a clients system, first thing I do is check available drive space...