>I think 2 walks is better as he would be so bored with just one per day and he is definately a full on sort of boy!
I don't agree that he needs two walks but it's clear that he needs some extra stimulation and brain work. Do you take him to training classes? A short training session will do much more to tire him out than a walk will. You can also have play sessions with him in the garden. It's really helpful to teach your dog that you are a source of fun and it's another thing to add to your recall toolkit when the "la, la, la paws in my ears" phase hits.
Remember to continue your socialisation too and take him to new and interesting places so that his walks are mentally challenging as well as an opportunity to let off steam. At this age it's tempting to think your dog is ready for much more but too much exercise isn't wise :)