I found that aswell i.e. it can depend on the type of dog food you have chosen and what the manufacturer says.
One food I had my cockers on, a rep for that company insisted that the puppy would need the extra protein (30%) and that the puppy should stay on puppy food for 12 months before switching over to adult food.
The food I have my dogs on now only has 20% protein and they believe a puppy should switch over to adult food at 6 months. I am actually getting a new pup in 5 weeks (not counting

) and that's what I'll be doing.
Also some manufacturers have Senior foods while others don't. Who is right? It can be confusing.
Anyways when I get my new pup I am going to switch her onto Adult food at 6 months.