Even though I only used one of the two packs, it still lights up. I hope so because it's been a month at most. They were a bear to climb out of the plastic seal attached to the two boxes they are in, but it's better to have them boxed almost too well than to have them fall out of the box just to look at them , or? Durability is one thing. they want to be evaluated along with the packaging, so in the paragraph above. I use these lights on 24" aquarium strips. I haven't had any real algae growth and decided NOT to attempt to grow live plants in this tank due to its height. The tank is 45 gallons high so the water depth is 36 inches. Test this Lamp against a well known brand bulb that was significantly more expensive, both bulbs at least being "equal" in numbers. This bulb gives a significantly deeper and less shadowy glow than the "famous brand". A branded bulb is 3-5 months old, maybe worth considering.