After 6 weeks of 'CPDing' there is little doubt in my mind what is the most beneficial use of that time: observing other teachers. And it really doesn't matter what stage. I am P3, but I have observed, in my own school, P2, P5 and P6. My deputy head also arranged for me to visit another school where I was able to observe my own stage, and they were sooo nice to me(!) They said come back anytime. Only my bookie normally says that. It was incredible.
The only downside was I found it left me feeling quite humbled and like an inadequate gonk just out of University (you are - Ed). Why was Miss X's class so quiet? How many plates was Mr P spinning at once? You pick up tips, strategies, looks, lesson ideas, ideas for quick finishers, vocabulary that works, good jokes, bad jokes, blue tac and sweets. Obviously I love my 6 hour lectures on the importance of not befriending five year olds on Facebook, and how to suck an egg, but for sheer usefulness it has to be an observation.