Cracked

Above our kitchen there is a glass balustrade.  It has been there for 4 years.  The other night, without warning or obvious reason, it shattered.  It made an explosive noise and, while most of the glass stuck together, some fell down into the kitchen.  No-one was there at the time.  It was more than a little disconcerting.

Today, the glass man thought he was being reassuring by telling us it was very rare but spontaneous shattering does happen.  So it shouldn't happen again, should it?