Which light have you used the most / run the longest?
At first, as EDCs, my mainstay was a ’502 with XP-L (5000K or so), and then my current MH20 in NW, whatever it has under the hood.
I rotate through so many different lights in the house, by function, that I don’t think there are any clear “winners”. So my diffused Tacklife in the kitchen or down in the basement, DC7/SP47/IF22A/TM03 in the living room, i1Rv2 on a lanyard around my neck if outside and no pockets, etc.
Probably my Starry Light becasue i was using its moonlight nonstop when i lived in a basement. Though its threads are stripped so its had less than an hour in the last 5 years.
Next would be my Xtar Moon RC2, the battery lasts forever on a charge.
My first Convoy S2+ was in SST20 4000K - I then proceeded to buy my next 5-6 lights in that same emitter and temp. By far my most burned LED.
xhp35 Hi is the best emitter ever in the history of mankind, change my mind 
Bort could hypnotize you to think you are a chicken.
That doesn’t change your LED preference but it would change your mind to a different species
The Sofirn C01. I have more than one, but the first one was in use for hundreds of hours. The LED became increasingly rosy over the time. They’re aging well.
I EDC'd a FW3A for years, but I did not use it for all that many hours.
I mean, I would use it pretty frequently, but not for very long each time.
Convoy M3-C for walking at night. Mine seems to hold turbo forever in winter. XHP70 5000K.
Pound for pound, The Sofirn SP35 with SST40 puts out a lot of throw and lumens in a small package.
SST 40 in the Sofirn SC31 Pro is my EDC.
XHP50 in the Astrolux EA01 and Sofirn SD05 are great too.
Probably the Samsung LH351D. Between my BLF SP36 and my SC64C LE that emitter has pulled double duty as carry and walking light.
I think some other LEDs have been catching up though. Lately I carry my D4V2 in E21A a lot. And some days the thicker body of the SP36 gets passed over for a slimmer light like the SC700D and SF47. Winter is a great time to use the SP36 though—it can double as a had warmer!
Weird, mine cuts out at maybe 70% battery charge. I can only run it about halfway till the battery is empty (step 3 if you use stepping mode).
What battery do you use?
The emitter I have used the most is the Nichia 219B
When it came out I put it in my most used lights
I have lights I have used as bike lights since “12 or ’13 , usually with the old XMLs , so those emitters probably have the most hours on them .
i have one of the very early Armytek Wizard Pro lights which originally had XML2.
This light was modded with a Samsung LH351D and it by far has the most burn time of all my lights, as it is often used for many ours when, soldering, tinkering, reading or when my wife does puzzles.
Now that i think about it my LED lightbulbs get the most use, averaging 12 hours a day until they burn out. Putting my flashlights to shame.
And my undercabinet light is also getting about 12 hours a day of use.
Thats 4383 hours a year.
Lightbulbs rated for 25,000 hours, they should last 5.7 years.
Undercabinet rated for 35,000 hours iirc, so in theory they will die in 7.99 years.
I am using the QB 26800 6800mah battery. Turbo drops out at about 3.7 volts. I was talking about holding turbo without thermal stepdown. I can not see any stepdown in winter and only a small stepdown in warm weather. Level 3 in stepped mode barely gets warm. Level 4 gets hot but not uncomfortably hot.
Ah, i am using a 4500mAh 26650.
Does the 26800 fit or do you have to extend the stock tube somehow?
I use level 3 the most as you say its stable the whole runtime. But for the wow factor level 4 is amazing on a fully charged battery.
Convoy flashlight store sells short extensions in different colors for a few bucks.
here’s the battery
Thanks 
My 2000K E21A KR4. It’s a bedtime light that sees nightly usage.