Two things that will shorten the life of an LED:
1] Overcurrent. Meaning the light control unit in the light itself (called a driver) is set to allow too much current to the LEDs. This can be, for example, driving 1 watt LEDs with 360 mA current when they are designed to handle only 350 mA. This leads to the second life shortening item. Yes, you can overdrive LEDs by quite a margin, there are many ways to do this. However, you will also need to add active cooling.
2] Cooling. You would think that being in a submerged light unit, they would be cooled by heat conduction into the pool water. Not necessarily true. There has to be a complete thermal path between the LED and the pool water for this to be effective. Chances are that there is not, due to electrical isolation needs for the pool environment. So the LED light manufacturer has to make certain compromises, and heat conduction would be one of them.
Normally, modern state of the art technology gives us LEDs that still need a good way to shed excess heat from the LED itself. If the die (the part that actually emits the light) can't shed the heat, it's life is shortened exponentially. So an LED that is rated for 50,000 hours will destroy itself in as little as 500 hours if the internal temperature goes even 15% over the design specs.