It's hard to estimate. First, those bulbs in downlights are difficult to replace, but that's not the bulb's fault! How long bulbs last CAN be judged and I've had very mixed experiences with the same bulbs from the same manufacturer in the same packaging. I've had lightbulbs that worked for years, and then I've had a bunch (perhaps defective packaging) where they often burned out, sometimes just two weeks. This last batch seems to take longer. I hope this continues. As already mentioned, they are not easy to replace!