Hammerer:
I saw several cheap LED downlights with plugs to the driver unit and long warranties (like 20 years) so I bought very cheap when on sale. It has been a simple job to detach a defective downlight (1 of 8) and connect the spare unit I'd bought. The spare downlight confirmed that it wasn't the driver. Then I took the defective unit to the store and they immediately replaced it without testing and without any quibbling.
It's good they have the straight swap out policy but I'd see this as it being a common product fault if they're not testing them for anyone that just comes in and drops it off for a swap. I have good relationships with lighting shops and they usually at least test it out in front of me to confirm a fault (even though I've done this myself before bringing it in)