I don't think the carbonator caps are durable or well made. It's easy for a 2L bottle, empty, with a cap on it to fall, because they are top heavy, and then the cap breaks. I have a cracked one. Another complaint I have is they tend to leak when attached to co2. In other words, they work fine for me to put pressure on a 2L but not to leave hooked up to my gas lines. I have 3 of these things, one is cracked and the other two I am paranoid about now. My local HBS told me they've gone through a few generations of the product due to breakage.
Dunno, I've been using the same two for several years and have dropped the 2 liter bottles more than a few times without damaging them. A leaking carbonator cap is usually caused by a worn O-ring. Just like with a keg post, you need to replace the O-rings occasionally and lubing the O-rings really helps minimize the wear and tear.