good point....sometimes its hard to get correct information from the seller because all looked almost the same in terms of its brightness when its new. But when time passed you will notice those cheap LEDs brightness will dropped significantly. I'll said 3 months. Good quality LED will maintain its brightness loss in less than 3% annually. (correct me if im wrong)

AFAIK it's case by case on different brand.
Some branded manufacturer do have this kind of warranty but not those rojak brand.
And remember to ask what type of warranty they giving (1 to 1 exhange or send back for repair)

lots of choice for that budget. But it usually won't last for more than 2 years (depend on your luck)