If a carboy breaks because you put hot water in it, its a piece of crap. I have taken carboys from temperature extremes so many times and never had any break or even crack. Don't buy the thin cheap ones and you wont have this problem. I have never broken one and I will admit when I first got into the hobby I handled them while completely smashed. I actually enjoy the possibility of the carboy breaking...kinda like a juggler with chain saws or something...It adds an element of risk that I somehow find exhilarating. With that said, I would like to move away from them eventually but I have some really nice ones and I would hate to stop using them for no reason.