Ok so I got this idea not while showering, but because I’m very high. The story does come from my bathroom though! I have a night light in my bathroom, and I was looking at the night light as I turned off the bathroom light. I’m a big nerd so I remembered that the things that detect light levels are actually diodes wired in reverse. I thought it would be funny to make it flicker by reflecting the light back on the diode, but it didn’t work. That’s when I had this realization
Heat does affect diode lifetime. So brightness/duty cycle certainly does affect how long it’ll last, because more energy going through means higher temperatures.
But with any light/fixture that has sane heat dissipation, it’s not worth worrying about. LEDs will last decades in most scenarios.