Ever since we moved into our house about 5 years ago, it seems like light bulbs burn out too fast in some of our lights. It's not bulbs in lamps that burn out fast, it's bulbs in some light sockets in the ceiling. I haven't done a careful check yet, but it seems like they only last about 30 days. Any ideas why bulbs would burn out faster in some light sockets but not in all of them?