I had that problem with some of my older jewel cases, when I used the CDs all the time before I started ripped everything to my computer. Or worse, one of the small pieces that the cover rotates on would snap off and the entire thing detaches.
Some jewel cases are made from thinner plastic and will break rather easily. But, the benefit of jewel is that you can take them apart and move everything into a new case. Can't do that with digipacks.
That is true, but the problem is that that means I'll have to sacrifice one of my other albums to take jewel case parts from it. Unfortunately, I don't see very many good quality blank jewel cases for sale, especially now.
Generally speaking, I've never had any problems with digipaks breaking or anything of the sort. Usually it's the outer part that gets damaged because of having other CDs on top of it, or something of the sort.
The only digipack that I had crack on me was JLB's Elements of Persuasion, and that particular digipack felt like it was made a bit cheaply.
Plus, these days, some digipacks don't even come with plastic bits. They're pretty much just envelopes, so there are no parts to crack at all.