I have previously had regular SS bulbs last years.
The Sylvania LL bulbs have lasted me years (2-3) but I don't get that out of the 9004 silverstars.
In addition to just not lasting as long, my guess is that it was a combination of bad battery and rough dirt road I drive on every day. Also, I drive with my headlights on.. so thats about 1.5 hours a day. Most of that time is spent on the freeway so the voltage is at the 14.0ish V area, and not the 13.0 area (13.0 v when a/c is on max, trans cooler fan is on and stereo is on at idle)
I've had a bouncing volt meter for over a year. It wouldn't happen all the time, but it was anoying. I'd see it happen once or twice a day. Basically the volt meter would drop from the normal 13+ area to < 12 area.
The road I have to drive on is a somewhat rough dirt road. It has washout across the road, bumps, camber transisions and more. To make it "feel smooth" I drive it 40mph+ (slow down to 30 for the big dips), but it ain't smooth, just not a constant rough.
After giving up trying to find a bad wire I took the battery in to be tested and it tested at 70% so I got a new battery. I put it in, and no more bouncing needle. My guess is that something in the battery was moving on the hard hits which shorted it internally.
I also changed the headlights right before the battery (couple months) and so far so good... Of course, now the explorer isn't the DD so all bets are off (been retired 1 month).
We ran the Silver Start 3157 (I think its 3157, the one with the flat connector) for brake lights on our '06 mustang. They lasted just under 1 year. I have since switched to LL bulbs as we don't need it as 'bright' since the brakes are modified to turn on all 7 lights when you hit the brakes. So far so good, the LL lights are lasting. Oh yea, to change the brake lights on the mustang required you to remove trim panels, factory subwoofer, factory amplifier, amplifier bracket and then the light assembly. I don't want to change lights on that car.
before anyone asks, yes I wear gloves when I change bulbs.. I wear 2 play nitrile gloves.
~Mark