I've been in my rented flat for 4 years, after 3 months the inner glass shattered after I used the grill with the door open, I thought closing the door after use straight away was the problem, since then, I always left the door open ajar after every use for 10 mins so that the glass has time to cool, however 3 years of doing this was fine but the glass has shattered again. I cleaned the glass a few months ago by taking it out so I think I may have screwed the metal washers a bit too tight. If you loosen them slightly, the glass wont fall out but it will provide ample room for the expansion of the glass.
Austin May (Bedworth), April 2013