Low beam problem on 2002 Volvo S60

I've been having a problem with the low-beam headlight, on the right side only. Every time I replace the bulb, very shortly it's out again, within about 2 weeks. So far I've replaced the bulb twice, thinking ok, maybe it's just burnt out. But it will occasionally come on suddenly, for a short while, and then be out again. I've had no problems with the left side at all, haven't even needed to change that bulb. Could this be an electrical/connective problem? Bulbs are expensive, I can't afford to keep replacing them.

2 answers
Do you have regular halogen bulbs or are they HID bulbs?
Are you being very careful not to touch the new bulb when installing it? Do you see any water inside the headlight housing?
Buy the Osram/Sylvania H7 bulbs that marked LL (long life) the rest will burns out quickly. The correct one: H7LL We don't even stock other bulbs anymore.

Zee