I bought 5 toner carts (3 color and 2 black) 1.5 years ago, and just now used my last black one and found that it's defective. I called and the best the supervisor would do is 10% on buying another one.
I talked with their Department Head and explained to him that there's no practical way to determine whether a cartridge is defective before using it, and often on toners it takes a long time to use it. Thus, on a product that has basically an infinite shelf life, it doesn't make sense to have a limit on the warranty. He agreed with my reasoning, but refused to make any exception other than the 10%.
I think this warranty limitation is a very customer-hostile policy.
So if you buy from this company, I'd suggest that you make sure you install everything and try it before the warranty runs out.