Craig,
Since I got up a bit early today, I will answer, but Shane et all, please correct me if I am wrong.
Tools, not accessories, are covered under the 3 year warranty. However, unless the systainer was damaged from the get go, there is really nothing to "wear out". You can certainly crack the systainer (it is plastic, tough plastic, but still plastic), but even with a cracked edge or torn insert, it should still serve it's purpose (storing/protecting/transporting) tool. As a side note - I have yet to crack a single systainer. Latches are always sticky at first - a shot of WD-40 or some other type of lube, eases that issue immediately.
Systainers are a good thing - just makes storing/protecting/transporting the tools easier and takes up less space in the shop or truck than having all those odd shaped tool boxes laying around. And if systainers weren't so useful, other tool manufactures (Lamello for one) would not have opted to have them designed for their tools.
Bob