Headlights going out

[Nero Morg]

So between my roommates car (2003 jetta wagon) and my dad's car (2001 jetta sedan) both of them have issues with just the left headlight repeatedly burning out. As in like I've done a bulb every other month.
With my dad's car I even went to the extent of replacing both of the entire assemblies with the headlights that came off my car. Still popping bulbs. Is there some ridiculously silly thing that can be causing this? Changing out the drivers side bulb sucks with the battery right there.

Both cars are 100% stock in regards to lighting, DTR not disabled.

 

[ToxicDoc]

first thought is bad grounds causing increased current draw. find grounds and clean them

 

[Nero Morg]

I had cleaned the ones on my dad's car when I swapped engines on it, but not the 03. I'll recheck them.

 

[STDOUBT]

Greasy fingers on the Halogen bulb glass? Yes they'll pop!
Seriously though I know it can't be that