Why dual filament bulbs on Silverado DRL's

I have been discussing this topic in another thread and there seems to be some confusion. Why is a dual filament bulb used on the daytime running lights on the chevy full-size vehicles? I have verified on my
2000 Silverado that only one filament is used for the DRL's. I have tested them with the turn signals on and the parking lights on and low beams and high beams. None makes the second filament turn on. One poster suggested that it was for the flash to pass operation during the daylight (when the headlights are off). This might be but is impossible to test by myself. I do know that when you flash to pass, the high beams are activated for sure but maybe the second filament in the DRL is activated too? If so, that seams like overkill.
The reason this all came up is because I was wondering if the life of the crappy DRL bulbs could be extened by flipping the bulb over in the socket and switching filaments. If the second filament is never or rairly used, I thought it would be a neat trick to extend bulb life. Or at least a temporary fix so that you don't drive around with a truck that looks like it has a black eye.
I have also read that there is a heavy duty replacement that should last longer. What are the numbers of that bulb? Anybody with experience with the LED replacements? For the price they better really last forever.
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To test light operations when alone, park in front of a store that has windows that go down to the ground. 7 /11 for example.
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