I think the discussion in Jordan's blog is more towards the American market. In any case, in my view there is no clear answer and it really depends on the circumstances. However, it seems to me that in Europe the dates when postdoc positions start and end is almost random. In lots of cases postdocs have no teaching obligations so the starting and ending dates could be quite flexible. Also most people are quite understanding of the difficult situation postdocs find themselves. So I think the best thing to do is just to talk to your current supervisor / employer and ask for their advice. Also if you get an offer from some place you can ask them how flexible they are willing to be about the starting date. In many cases they will be very flexible.