Remember your new pup has been bred and born to retrieve, mark falls, swim, smell things (good and bad) and a whole bunch of other wonderful things that make it a hunting dog .The one thing it wasn't born with is obedience, that's the one big thing that was left for you. If you spent the entire first year on disipline, developeing memory, socializing and getting your new friend to trust you , You would be miles ahead of most trainers. In my humble opinion I would say it takes at the very least 3 years of decent training and enviroment enrichment to end up with a good duck dog. And the training never ends.
Don't get too hung up on a time schedule and in saying that, the sooner you start the better. Mom wolf has the whole litter trained to DO NOT MOVE, DO NOT MAKE A SOUND AND DO NOT CRAP IN OUR HOME before they are 4 weeks old. Take it from there. And one more thing, you could never expose the pup to eneough situations and shoot enough birds in nine months to have a finished retriever----So don't be in a big hurry.
I'm not as good as I once was, but I'm as good once as I ever was.