LED suppliers quote figures like 20,000 h or 30,000 h. Those numbers are useful, but only if you know what they mean in practice.
What the rating actually measures
LED lifetime is normally quoted as L70 (or L80): the hours of operation at which output has dropped to 70% (or 80%) of the initial value. It is not a sudden failure point — the lamp keeps working, just dimmer, and the number assumes controlled junction temperature and rated drive current.
Three things that shorten it
- Heat: the dominant factor. A head run without adequate cooling ages far faster than the datasheet curve suggests.
- Overdrive: pushing current above rated value buys irradiance and pays for it in lifetime.
- Duty cycle: continuous 24/7 operation at full power is a harder life than intermittent bench use.
Three things that extend it
- Dimming when the process allows it — output and life both scale with drive current
- Clean cooling path: filters changed, water flow checked, cold plate clean
- Running at realistic line speeds instead of full power against a stuck conveyor
What “end of life” looks like on the line
You will not get a warning light. What you will see is a slow creep: line speed has to come down a little, or cure needs a second pass, or the surface stays slightly tacky at the same settings. That slow drift is the real signal — which is why logging irradiance at scheduled intervals is more useful than counting hours.
Practical expectation
For our water-cooled industrial heads in continuous duty, 20,000–30,000 h to 70% output is a realistic range. Bench and intermittent use lasts considerably longer. Either way, budget for a head replacement roughly every three to five years in multi-shift production — and keep a measurement record so you replace it on evidence rather than on a calendar.
