I pulled the bulb off of one of mine (Luminus brand from Costco, not Fiet).
Still works:
Meaning there's no phosphorescent lining to the inside of the bulb, as I was starting to wonder. I can't see there being enough phosphor on top of those tiny chips, either (but correct me if I'm wrong).
Longevity seems ok, in spite of not having a huge heat sink. I've had to replace 1 that I know of in the past ~2 years, on lights that stay on 24/7. Not completely conclusive, but at least comparable to CFLs, which always seem to croak after a couple of years.
I'll re-purpose this bulb. 800 lumens at 9.5 watts (though double that volt-amp wise) for a couple of bucks? Drool!
Edit: They may very well have a phosphor lining built in to each LED...when you cut the power, the LEDs fade to nothing over a half a second or so. (or does the power supply have a capacitor that takes a moment to discharge?) Might explain the yellow you see on modern LEDs? (they used to all be clear just a few years back). Then again, I have red and yellow LED bulbs that are yellow on top.
Welp, I'm now thoroughly confused. Someone enlighten me!
Edit: it inst a persistent glow, like a CFL...I'm going with capacitor discharge.