TOPIC: Encrypted File Cache Becoming too Large

Since we have recently released this the eBook cache is growing at a high rate:
/wp-content/plugins/ebook-store/cache = 23GB

We have encryption and watermarks enabled and I presume all eBooks sales are creating duplicate versions of themselves (various password and watermarked versions) to be available for the download link at the time of the sale and stored in cache (based on the files I see there).

Does "Link Expiration" or "Downloads limit" allow for these files to be purged automatically on any period by cron or other means to keep this folder at a reasonable size? OR will this folder just keep growing indefinitely?