[Morbo the Annihilator]

Hi, I'm new here.
I found this place by googling around for answers to the following question. I recently discovered cracks in both my 14" and 16" Zildjian Avedis Fast crashes. I've had cracked cymbals before but all my previous ones were cheap crap. The setup I have now (and spent alot of effort and money to put together) I believe to be of considerable quality. I've been drumming for quite a long time now, but never really looked into what could make cymbals crack and if it is "normal" for them to crack after a certain time, so I'll just explain the whole situation.

The 16" is about 3 or 4 years old now, but I've only had the 14" for about 1.5 years.
I live in an old house with very low humidity, but it does have very unreliable heating, so temperatures vary. I use 7A size sticks, and consider myself to hit fairly hard while playing, but not really extremely hard. I play all sorts of music, and the hardest my drums have to cope with is probably punk rock, which is my "main thing". I play gigs with my band quite regularly and have a bag to carry my cymbals around in. My bandmates view me as ridiculously careful when it comes to carrying them around. I never put any weight on them and always ensure they're flat and on top of a regular surface (mostly my bass drum), among other things.

So, enlighten me, is this something I'll just have to put up with, is the environment (as in my house) doing this, or are those cymbals just crap (that would suck, because I love the sound of those two crashes)?