Capital Lighting-Spencer - Four Light Outdoor Wall Lantern Old Bronze

We purchased two of these lights in 21" tall bronze. They are the perfect size and design and what I was hoping for until 24 hours after they were installed, one of the glass inserts broke!!!!! What a disappointment for such an expensive light! We have no idea how that happened!! Our lights are under a front porch and not exposed to the elements. It has not been stormy or windy. I placed a 75 watt light bulb in them and the light itself says it takes up to 100 watts. The lights were on all night, as front porch lights typically are for security reasons. Could the glass have gotten over heated? You would think a porch light could stay on from 10 PM to 6 AM without breaking. I hope Lamps Plus will send me a replacement piece of glass. Extremely disappointed!!