How long is a postdoc?

I was awarded my PhD just under two and a half years ago; I’m a little under a year and a half into my first postdoc, and potentially have funding until the end of 2009. I’m working in a laboratory that is about to go through a major upgrade, which will give me lots of shiny new toys to play with, and increase the range of measurements I can make, and the speed that I can make them at, by orders of magnitude. I’m currently at the ‘optimistic but suspicious’ stage with the data I have so far – it’s saying some potentially interesting things, but I’m still not sure I’m not being fooled by evil magnetic overprints (if my PhD taught me anything, it’s that you should never blithely assume that the primary magnetic signal dates from the time the rocks formed, and if that’s true of 10 million year-old sequences, it’s no surprise that I’m treating my 3 billion year-old samples as guilty until proven innocent). I’m also trying to spin up a side project that will try a new approach to studying the inter-relations between magnetic mineralogy and magnetic behaviour, which could yield some pretty interesting results if it works the way I hope.
On the whole, then, things seem to be going fairly well at present. But I also need to consider my progress in terms of my future career goals, which (if I stay in academia) would see me in a more teaching-orientated position such as a lectureship or teaching fellowship. I’m fully aware that a solid research record is a necessary requirement if my applications for such positions is going to be seriously considered; but what I don’t really have a good feel for yet is how long I need to work as a postdoc (or perhaps more accurately, what sort of publication record I need) before I will be considered ‘established’ enough. I was recently told that five or six years would be a reasonable waiting period before I can climb to the next rung. I’m hoping that my pre-postdoc position as a lecturing lab technician will count in this calculation, but even then it looks like I still be waiting for a while. The question then becomes, how should I spend this period? Obviously, I need to publish; I need to try and broaden my research expertise; and I need to try and build my visibility within the research community. But what is the most effective way to do this? Should I stay in one place, which might allow a more consistent output but might limit my interactions with other scientists; or should I try to move around a bit between other labs to sample a greater variety of environments and approaches to research, but with all the disruption that comes with periodically uprooting myself?
A lot depends on circumstances, of course (for example, there’s no guarantee that I could find a research post in another lab even if I though it was a good idea), but knowing what the best path might be would still be useful. Perhaps some of you smart people, whether pre-, syn-, or post-postdoc, have some thoughts or relevent experiences to share. How long was your postdoc, or how long has it been so far? What experiences or achievements were, or are, important in making you competitive in the hunt for permanent or tenure-track positions? Do you think one or two long postdocs is better than multiple short ones? Does the present academic job market doom me to eternal postdocdom?