Yesterday, this question was asked on twitter (yes, I suck at embedding tweets here...):
@GenomeDaddy (Another) postdoc: yay or nay? I guess that's basically where I'm at now.
My answer was that a second (or third perhaps) post-doc can be a good things. In my opinion, there are several reasons why you want to do another post-doc: the best reason I think is to learn another technique in order to be able to independently conduct the kind of research that you are interested in. Another reason for a second post-doc is to switch labs to somewhere better than where you were initially. And of course, doing another post-doc might be necessary, for example if your current lab doesn't have funding anymore, closes down, or when you're part of a two-body situation. Because I understand very well that doing another post-doc is always better than having no job at all. In that case, it is important to find a lab where you do not have to take a step back in autonomy, as I found that to be a very frustrating situation.
I was a research associate for the last year when we were in the US, and even before that, I could pretty much do the experiments that I wanted to do, despite not having my own funding. But at some point, due to a bunch of factors we were moving back to the homecountry, and because I was unable to land my own funding before that, I found a job as someone's post-doc. But I can tell you now that coming from years of deciding on your own which experiments to do, and supervising summer students and technicians, it is a rather frustrating feeling to have to do someone else's experiments. Especially since the grant that I am on now is so short that really everything has been planned and I am basically reduced to a set of hands to do the experiments. Add to that some other things that I am disgruntled about and I can tell you this is not an ideal situation. I think I would be able to wait this out, do the experiments, and in the meantime continue to apply for more funding, but as I told you recently, I decided not to. I realize very much that moving out of a post-doc into any direction is tough and I feel lucky that I managed to do it.
So to conclude: another post-doc can be a good thing, but it can also be a frustrating thing. In which case you need to decide if this is what you want - or need - or if you need to explore other options.