Why do tail lights always go out at night?

So yesterday I'm working late and reading about getting red lights to change (while waiting for a compile to finish), and I decide I'll go visit the one traffic light that never changes for me, just to prove once again that starting the bike, putting the side stand down, and all those other myths don't work for me at that light.

When I'm ready to leave I have plans for some additional hooligan behavior as well, and when I turn the bike on the tail light is out. I know I checked it a few days ago and it was working, and it was only about two weeks ago that I cleaned the contacts on the bulb to make sure the light wasn't intermittent.

So I changed my plans and rode the two miles back to my house carefully, trying not to be in front of any cars and to have my brake on the whole time I'm stopped at any intersections so that there is a light on.

It seems like I was just installing a new bulb a few months ago, but I realize that it was at least a year ago that I put the previous 1157L bulb in. Since those come in two-packs, I found the other one in my "electrical parts" drawer out in the garage.

I took the seat off, removed the two screws from the red lens, and took the old bulb out. Sure enough, one of the filaments was broken. As a side note, I also realized that my teenage son has managed to lose all of my phillips screwdrivers, so I had to use a Swiss Army Knife to remove those phillips screws.

I found a trick for better bulb contact: sand or file off a little of the surface on the two bumps that bring power into the bulb. That helps reduce the chance of intermittent lights on bumpy roads.

I've had problems in the past with inserting the bulb backwards so that the brighter brake light is on all the time and the dimmer tail light makes no discernable difference when you apply the brakes. I tried inserting the bulb both ways to see which seemed easier. On my particular bike, it's easier to get the bulb in backwards than the right way. Amazing! So at least I checked the behavior of the light first to get it in the right way before tightening things up. All Monster owners should check this when installing rear bulbs, before you close it up.

Anyway, since it was too late, once I got the tail light fixed, to go out and participate in some night time hooliganism, I'm still feeling the need. Maybe I'll go do something at lunch today...