These models are just a poor design, basically using the brighter (brake/turn) filament of what is a common tail/parking bulb versus the headlamps. Most dual filament bulbs list 1000hrs or more for the dim filament, and 150-300 hrs for the bright one. The industry number for the bulb has changed at least 3 times over the years to try to come up with a bulb that will last. DRL's are not required in the US, they are allowed, and the owner choosing to use them or not, if switchable, or disconnecting them is perfectly legal. Most states laws require any factory exterior bulb to be functional, so driving with one out can net someone a ticket, but disabling them is ok. There is one cash strapped town close to me that writes between 4-10 tickets daily, every day just for a single DRL showing; mostly GM trucks. My wife's TrailBlazer uses the 9006 low beam as a DRL, and it does not burn out often, but recently I had to replace the bulb pigtails due to being burnt and the terminals distorted to the point of no longer making contact with the pins in the bulb. The TrailBlazer has the cutoff switch, but it defaults to on every time ign is switched off.