For me, the heart of this Thing is formal, recognized learning vs. informal CPD. The former is good for job hunting or proving something to yourself or other people but usually comes at a high cost of money and time (both to you and your workplace perhaps). The latter is more responsive and flexible, can be free, yet is hard to get recognized in the long run unless you can do wonderful things as a result.
I have a silly amount of qualifications amassed over the years. I did the library Masters purely because it was the only way to get a "proper" librarian job where I wanted to work - I'd loved working on the Issue Desk but I also knew I'd want to move on in years to come. As I was already maturing (like a good cheese), I decided I didn't have time to waste so took a leap of faith and went off and did it in a year full-time at Aber. I have to say it was quite a dreary course apart from the utterly wonderful Local Studies module (we begged for more at the end!), the more tekkie Internet Searching stuff and of course anything taught by the brilliant Geraint Evans (now
author) was worth attending. It did the trick and without the MScEcon I wouldn't be where I am today...
I did go on and get Chartered. I'm not entirely sure why, looking back - I think I just felt it was the logical conclusion if you were a librarian...I'm not too sure I'd feel that now? I enjoyed the discipline of it and the reflective practice. I also did it at a time when I wasn't employed in a library (I was an e-learning advisor for a few years) so it meant I kept a focus on librarianship.
I would only do another work-related qualification if I was very sure it was going to be interesting and practically useful. A teaching course is the one thing I'm pondering at the moment as I'd love to have a better understanding of teaching theory and improve my practical skills (which have all been learned on the job). However, with two small children and other things that need to take priority (learning Welsh to keep up with my son's homework), I can't see it happening for a few years. Otherwise, I try to research and learn about things as they crop up in my job - I've just been scanning around for any good practice or ideas on library inductions as tomorrow we are discussing what to do different this year.