Well, at one point some months back, I was pouring hot water into the mug (because that is what ceramic mugs are for) and it made a distinct popping sound. I checked and could see that it was indeed cracked but as it was not then leaking fluid I continued to use it. Today, however, the recurring popping sound was accompanied with a flow of liquid out of the side of the mug.
I should very much like to have a replacement as, I have said, it was my favorite, however I cannot in good conscience do so without some sort of assurance that the replacement will be more thermally sound.
I shall have to return to conventional mugs that lack the facial hair protective guard.