This is a problem which I've lived with for ages (see below), but I thought I'd raise it here to see if anyone else has experienced it or has any solutions.

I've owned a 1.9 tdi Fabia Comfort Estate (02 registration) from new and it has now done 150,000 more or less problem-free miles. During that time, I would estimate I have replaced/had the garage replace the near-side front side light bulb at least...oh....30 (THIRTY) times: after a (not very long) while, it gets dimmer and dimmer and then - sometimes after 2 or 3 weeks of hardly glowing at all - it just fails. When the car was under warranty, I mentioned it to the dealer but, perhaps unsurprisingly, it never seemed a big or expensive issue and they never got to the bottom of it, despite several mechanics having a go and cleaning various bits and pieces (I'm not technical myself, unfortunately, as that probably makes clear!)

It's just gone yet again - this time after just two weeks - and the irritation of having to go out in the cold and change it made me write this!

By the way, the headlights on the car seem to have a relatively normal life, but I would say that the other side light isn't particularly long-lived either.

This will be a poor bulb earth, either in the bulb holder itself, or in the wiring loom. If it were a voltage problem, it would effect every light on the car. It's varying voltage that kills bulbs, as they are designed to run at a constant temperature. If the bulb element has irregular voltage it will blow quite quickly in its life.

I would bet its actually a faulty bulb holder assembly, which is part of the headlight assembly.

Seconded- Moggytech has said exactly what I was going to.

Thanks to both of you for such a quick diagnosis!