LED lamps don't 'pop' like halogen lamps they gently fade away. You'll hear claims that they last "50 or 100,000 hours" Whilst this is technically correct they will end their usable life with less lumens output than they start out. The scale of deterioration as a rule of thumb (although this may vary from lamp to lamp) is about 5% for the 1st 1000 hours then about 2% for every 1000 hours after. So a lamp with 20,000 hours on the clock will be around 25% less bright than it was brand new, When you calculate the energy saving over the period of the usable life you will still have saved a massive amount in power usage and the cost of the lamp will be well re-paid so as an alternative to halogen or incandescent it still makes sense to buy LED lamps.