If the glass breaks where a glass clip/screw is situated then the clip has been tightened excessively. Glass needs room to expand and contract therefore we only advise that the clips are finger tight.
Wet logs on heated glass, a badly aimed poker or heavy slamming of the doors could crack the glass panels. The glass will not fracture from heat. Should you need to replace a glass panel please ensure you purchase a new gasket at the same time. Please check periodically that the glass clips and screws have not become loose.