I've noticed that my LEDs seem to have a bimodal lifespan. In parts of the house where we have many of the same kind, we went through a period early on where a few lasted much less time than I expected and had to be replaced, but now I've not had to replace any for several years.
There seems to be an element of luck with the cheaper ones. The ones in a batch that work well just keep going, while a small number fail relatively quickly. Once you've gone through a few replacements you are left with just good ones that just keep going.
In failure engineering this is called the "bathtub curve." Those early failures are called "infant mortality" and are typically due to errors in the factory. In 20-30 years you'll get wear out failures, as the components hit the end of thier designed lifespans. Generally in manufacturing any new product/process has a pretty high infant mortality rate which then gets worked out over years of improvements to design and manufacturing process. You can either do factory testing (probably what high quality LED brands are doing) or just ship the product and let the customer handle it.
There seems to be an element of luck with the cheaper ones. The ones in a batch that work well just keep going, while a small number fail relatively quickly. Once you've gone through a few replacements you are left with just good ones that just keep going.