David, Yes you most certainly CAN remove them and re-install! If you are careful they actually pull off quite easily. Here's the trick: Do NOT grasp the ferrule with pliers and try to pull it off or you will crush it and lock it on even tighter. Instead, get behind the lip/edge of the ferrule with some small side-cutting pliers and slide it off the end. It takes a bit of practice, but you will get it. When re-installing the ferrule the crucial key to the procedure is to get a good clean cut on the conduit. As Rapidrob has stated, use a "Dremel" or similar tool with a small metal-cutting (abrasive) cut-off wheel. Also (very important) wrap the conduit very tightly with a couple of wraps of electrical tape and make your cut through that area. In addition, sometimes I will trim down the outer vinyl jacket of the conduit VERY slightly so that the ferrule will slide on easier.
Good luck!
Michael