In normal cases, LEDs can last estimated at least 5 yrs whereas the driver will estimated 3 yrs, if u r lucky, it can be longer. This is only apply to those better and quality types especially CREE led. MR16 is those LEDs replacing halogen bulbs, using GU5.3 or GU10 socket. Downlight suppose to be in a fixture type, either round or square type. For warranty issue, only those reputated brands do provide. Some can be 1 yr, 2 yrs or 3 yrs. After warranty period if spoilt of cos cannot be replaced. As long as within the period, no 2nd thought, immediate change so long as the model still exist, if not, they will replace a new compatible model. why not u upload the photo of the type of LED downlight u hv now ? Perhaps I can advise further from there.