This can often be caused by factors in the environment it is kept. Any cased glass is at more of a risk. While it is most likely the release of stresses that have been there since manufacture it would normally require an external influence to cause the release. But it can happen spontaneously (i.e. no obvious external event, although their probably was one.)
Factors to avoid:
1. Storing in an airtight (or near so) cabinet. (Ensure ventilation holes at top and bottom)
2. Exposure to sunlight. Particularly thin beams of sunlight.
3. Heat from spotlights (Use LED spots, or fluorescent lighting if you can stand the effect on colours)
4. Immersing in a bowl of warm water, or under a hot tap. (Use tepid soapy water, stand glass on a cloth and bring the water to the glass with a cloth/sponge.)
5. Stubbing out cigars, or resting cigar/cigarettes on it.
6. Applying localised heat.
7. Polishing out scratches etcetera and spending long enough on one area to cause it to warm up.
8. Serving hot food in.
I have seen cased glass breakages caused by all of the above. Guilty of #8.