Can LD05 emitter become weak?

So far, i totally love my LD05.
Last week I pulled it out of my shirt pocket and it was on and fairly warm. I wasn't paying attention to what level it was in, nor know for how long it was on, but I'd estimate 45 minutes since the last use. Worst case scenario it was on high.....
Anyway, it no longer seems as bright as it used to, despite fresh batteries. I'm on my second set since the "incident" as it has a definitive lack of brightness.

What got me thinking was a thread awhile back about how 5mm leds, when left on continuously, would have a drastic reduction in output. Is it possible this could have happened with a high power led? Is it my imagination? I use the light every day, off and on in medium mode for 10-15 seconds for dozens of times a day. A set of batteries typically lasts a week, to give an idea of useage.

Book time is 1 and a half hours on high,hopefully it is your imagination,not much use if you cannot run it on high for a long period is it?

Let us see what the experts say.

The heat could have damaged the emitters phosphorous layer, resulting in diminished output, and, eventually, a burned out emitter.

Would this be at all visible using a jewelers loupe? Does it change color? Although, I wouldn't have one to compare it to anyway.
I rarely (maybe once a week) use the high level, and previously always smiled when it kicked into high gear.
I'll have to get back my old streamlight luxeon jr from coworker to compare it to. If it still gets it's butt kicked, then it's been my imagination.