It dims by no more than 70 % over a period of 25,000 hours. That’s 1041 days, and around 2 years + 10 months. That is if you kept the bulb on 24/7.
They’re expensive ($40 a pop) but eventually we’d save $3.9 billion in electricity a year and keep 20 million metric tons of carbon from shooting into the atmosphere. Plus, the 60-watt bulbs we use now generally last for only 1,000 to 3,000 hours, which means you have to change each lightbulb every year or two. If this new bulb lasts for 25,000 hours (and it could last for more), you could use it for about 35 years without buying a new one.