Topic: Knox / compacting vault

I’m using Knox as a secure folder for large files. I’ve come to reaslise that the vault does not act like a normal folder as in the folder size does not decrease when I delete files. I have tried compacting the vault but I had to cancel the operation because it was taking so long. The vault size is 112GB. Is the compacting process a long one or is there something wrong? If it is a long process is there an alternative way of dealing with a high turn over of old files that need deleting?
thanks