LED overpowering - where is the truth?

I am doing it from the beginning (first 5mm super-bright LEDs) and therefore I have gathered some information what will happend and what will not. I have used these at up to 100mA and many of them have served well... Of course, I have improved heat dissipation capabilities of such abused leds at first...
So, what about high power leds? I don't believe in fast death if higher current is appplied, especially when properly cooled. Few times I accidentally shocked high power led with more than twice current, and nothing goes wrong. Modern power leds have very low thermal resistance, so the cooling is not a problem.
My question is: If I don't need 100000 hours of life, do I have to operate at rated currents? I think I do not. In many applications the led will be used few hours or tens of hours (bicycle light, flashlight, and many else), so 100 or 1000 hours of life is reasonable enough...
I also take in account fast improvement of led technology, who will cry for 1W 20lumen white led today? I will let it go and replace it with 1W 100lumen one!

What is Your opinion and experience?

Thanks...

Thank You very much, I have made some calculations and I found out that CO2 would not be so necessary:

For example I will take Seoul P4:

Thermal resistance for star is 8,5 K/W
Maximum operating junction temperature is 145 C
If my heatsink will be good enough not to warm over 40 C (no problem), I can dissipate (145-40)/8,5 = cca 13W from led chip... It is a lot when I compare it with less than 3W of thermal power dissipated in normal 1A operation... So there must be another reason (besides efficiency) for 1A limit... (I know there are gold wires bond to the chip and they have a current limit too)...

But 2 or slightly more Amps can not overheat the led chip when sufficient cooling is provided... Common bigger aluminium heatsink must work, or some fan cooled heatsink...

I have some peltier modules lying arond somewhere, and have no problem to buy some cheap here... I was thinking about this, I got my first 89W peltier module many years ago (around year 2000)
But it is still better to use 2 leds than using overpowered led with peltier (due to peltier cost which is reaching the cost of led and more power consumption).

But I still don't understand why shouldn't be proper heatsink enough for cooling the led, if the led has 8.5 C/W plus heat resistance between heatsink and star 1 C/W and the cooler is for example 5 C/W and let there be 0.2 C/W difference between the place under the led and the rest of the heatsink, it is 8.5+1+5+0.2=14.7 C/W. If ambient temperature is 25 C and for 2A we consider 8W: 8x14.7+25=142.6 C. Max allowed temperature is 145 C so this should work... It is not ideal, but still usable - I am calculating with the worst possible conditions...
So with better heatsink (maybe air-cooled), cooler ambient temperature or little less current it should be OK. My bike headlight consists of P4 mounted on heatsink. When riding, the heatsink is air cooled (cold air-at night) so I don't see problem in driving the led at 1.5A for example...
Is there anything else I haven't calculated with?
Heatsinks of this size and at this power has very equal distribution of heat, the place under the led will not be much hotter than the rest of it. I am often dealing with 10x or more power and it is OK...

I found a mistake in my calculation - the thermal power for 2A will not be 8W, it wil be less because of power emitted as light (around 1,5W). So thermal power produced by the led will be cca 6,5W which gives:
14,7 x 6,5 = 95,55 C
The led chip temperature will be deep under limit...

Correction: (ambient temperature missing)
14,7 x 6,5 + 25 = 120,55 C
Still fine...

Here in Slovakia I can buy Peltiers for this prices - example:

from
15x15x3,3mm 8,5A/2,06V 9,2W for 3,17 EUR

through
40x40x3,3mm 10A/15,8V 89W for 5,5 EUR

to
62x62x4,8mm 30A/16,2V 267W for 19,83 EUR

The e-shop is also in Czech rep., but I don't know if they are delivering to other countries...

The peltier does not need to be driven at max. power, it will be very inefficient and also in real applications they are used at max. 60% or so. When cooling led, small peltier running at 10 or 20 percent of its power will be enough. When proper peltier is selected, it is possible to connect it in series with the led and it's cooling power will rise with current flowing through the led - very clever way... The heatsink capabilities must be correctly chosen, because the peltier not only transfers but also produces heat...

Yes, that is right!
But, only if the cold side is too cold... It is not necessary to freeze the led, but just to make the temperature difference between the heatsink and the the led equal to the temperature difference of heatsink to ambient...
But I have found a lot of nice and cheap heatsinks very useful with star leds, and that will be the way for my applications :wink: