New Puppy with a large puppy

Question
We have a 10 month old female GSD and have just brought in a new male SPinone Italiano.  The Spinone is now 10 weeks old.  The GSD is well socialized and a fairly submisive dog.

We keep them somewhat separated, feed the GSD first, keep the toys separate and the food separate.  We have begun letting them play.  They really go at it "biting" and jumping on each other. The GSD is great, she lies there and takes it for a while then gets him down.  She seems to know just how hard to bite without hurting him.  At times it does escalate and we break it up as it seems scary to us.  
My question is, when we let them play together, they never seem to let up.  It is always us humans ending the play session and keeping them separate.  The yonger one seems to never want to quit.  We've let them go at it for almost an hour and we tired of it, not them.  
The only way we can get them to relax together is with the leashes.  Otherwise they contantly want to play and fight and as i said, it appears to be the younger one that never gives up. We are of course concerned that the 70 lb puppy could hurt the 15 lb puppy.
Is this normal?  When do you think we can expect to see them relax together?  and finaly, are we correct to separate them or should we let them work it out to a conclusion.


Answer
Thanks for your question.  I would let the larger dog be the judge of when enought is enough.  Unless your GSD is getting tired of the little one (youll notice him nipping more and trying to move away)  then you should separate them.  Let them play 2,3,4 hours if they want you shouldnt have to separate puppies.  Yes they will disapline each other when something gets on there nerves but dont run over right when you here one yelp.  Just say a firm No and let them be.  They will never learn disapline from each other if they are separated when ever they have confrintation.  Puppies usually start to calm down at about 16 months of age.  So at this point the older one may not want the younger one around as much but still let puppies be puppies.  It is very normal for puppies to rough house and get pretty darn rough with each other so you shouldnt have to worry.  Hope this helps and good luck with them!

Kati