[For My Coby]

I know we've already talked about playing vs fighting, but I wanted to ask a question specific to me. Today, I've let my 5 month old Yorkie and my 10 year old Shi Tzu play more together than before. The Shi Tzu is very grumpy and the puppy is very puppy-aggressive. I'm always afraid that the older one is going to get fed up and hurt the puppy. Today, they did pretty good once I let them go for it. The article recommended earlier today helped. It let me know that the nipping, posturing, and humping were fairly normal. Tonight, Reggie, the older one, is definitely less patient than earlier today and is snappier. I'm sure he's worn out.

My question #1 is - do puppies really know when the older one is playing vs seriously getting annoyed? Is it safe to let an old one and a young one go at it and work it out themselves? Will the youngster know when he's on the last nerve of the older one?

My question #2 is - Coby has just discovered the joy of humping and the two of these boys have tried to out-hump each other continuously in play today. I do now know that is part of trying to see where they land in the pack as well part of social play. But I don't recall Reggie being so "intrigued" with it so young. Coby's being neutered in 3 weeks. Will that have any effect on that at all?