Start with duty cycle. A lamp that runs twenty minutes at a time cools between uses; a lamp that runs a twelve hour shift never does. The second case is the one that kills LEDs, because junction temperature that sits high for hours degrades output permanently rather than temporarily.

Thermal headroom is how much margin the design leaves at the top of that range. It is visible in the mass of the housing and the area of the fins, and invisible in the datasheet, which is why two lamps with identical quoted output can have completely different service lives on the same machine.

Sealing comes next, and the number that matters is not only the IP rating but whether the unit has a breather. A sealed lamp with no pressure equalisation draws air past its own gaskets every time it heats up and cools down, and eventually draws water with it.

Beam pattern is chosen by working distance. Flood for the area around the machine, spot for reach, combination where the operator moves between both. Choosing four spots because they sound stronger leaves the working area dark and the horizon over-lit.

Lumens come last, and should be read as a range rather than a number. A quoted figure is usually raw LED output at 25 degrees, not the light leaving the lens after optical losses at operating temperature, and the gap between the two is where most disappointment lives.