I've repaired quite a few tanks but in over 30 years now have never had a tank split or crack on me. Proper set-up and having a VERY solid base along with good tank moving habits are key to preventing this sort of thing.
On the plus side you can pick up a LOT of cracked and/or broken tanks for free...take them appart and then store the glass pannels/frames until you have enough to build new tanks out of. (works best with standard sizes of course)
People complain about the cost of glass for repairs so I don't understand why more people don't do this.