When we purchased our house, we changed the locks out. Firstly, we wanted to have new keys. Secondly, there were 4 knobs, 4 deadbolts, and 8 unique keys! I went to our local Home Depots and looked for like-keyed sets of knobs and dead bolts. I was fortunate and found two packs of two deadbolts and two knobs each (a total of 4 each), all keyed alike (one key will operate any deadbolt or any door knob). These were not top of the line knobs, but the ability to get into any door with only one key is really nice. I bet if you shopped around, you could find a pack of two knobs and two deadbolts that would at the very least allow you a backup means of entry if one failed again. Or you could store a spare key for the front door, AND one for the back door, in the garage...
