I have got a super 5 year old male gsd. hes a good natured dog, my first and only dog.  I read things on here about typical GSD behaviour and he's all that. But i see no sign of him "growing out" of his playing behavior that people said he would grow out of, his excitement around other dogs etc, hes too much for most dogs so only has a few selected mates, who he loves. All play is full on charging, wrestling etc.I am just curious if this is normal or is he the exception to the rule! did i get the nutter! no regrets though , hes my best mate. sad eh!

OOOh yes!  My Belgian lad is exactly the same (4 yrs), total nutter, but hilarious with it!!

I have noticed quite frequently, that only dogs do have a tendancy to be more exubarant with others they meet than those in a multi dog home. It is the excitement for some of seeing their own kind. You may have to wait until he is about 7-8 for him to just be a nice calm dog, or if you can meet other dog walkers very frequently so that he is not quite so excited to see them.

Remember all dogs even though most stick to breed traits, also have their own personalities, he obviously loves to play and being large can only have selective playmates, is he interested in balls or dummies by any chance, my brothers youngest GSD is a very big boned boy and was extremely excitable I just used to stick a dummy in his mouth if he got too excited, and got him to play retrieve with me to keep him away from smaller dogs, but he has always had my girl and my brothers other GSD for play so not quite the same, but distraction is the key, with a loan dog you need to be his playmate, I've often had a good wrestle with my brothers GSD's it is what they like to do, but obviously many dogs are afraid of the size and play techniques so perhaps it may be best to lead him if you notice him getting excitable and encourage him to play ball or some retrieval games instead. :-)