I purchased 4 of these locks 2 to 3 years ago. At first they all worked great and I thought that I had really found the answer to keyless entry to our home. I have several people that need access to our home while we are away on vacation and keeping track of who has what keys is a hassle. Now 2 of the 4 locks have quit working...new batteries no help. I think that the gears or whatever have worn out. They really don't get that much use...maybe a couple times a week at the very most.