Yep, 2000 Td5, left hand side, I asked an auto electrician and he said the left hand side bulbs always blow quicker because the LHS of the vehicle always gets the rough drains, kerbs etc as you drive, whereas the RHS is pretty smooth.
I see where he is coming from but I find it hard to beleive. And its only the brake light. I suppose the brake light does get used the most!