Question about "dog play"?

We adopted Winston (3.5 YO male) about a month ago, and it took a couple weeks for him to start showing any interest in our other two. Well, now that Ollie (1.5 YO very active B/T) thinks he is half interested in him, he will not leave him alone. They constantly wrestle and play fight, which I love to see....but...

My question is, how do I know that Winston is actually *enjoying* this? Ollie is very rowdy and bites at his ears and neck to instigate play. Sometimes Winston tries to run away, but Ollie keeps at him. Winston is so easy-going, how do I know he will put a stop to it if he gets annoyed?

If my dogs are indication - then you'll know when Winston has had enough. Oz constantly wants to play and tries to engage Madison all the time. For some reason, she is his first choice. Madison will either play or just ignore him, and when she's had enough of his biting her ears, dancing right in front of her face, and body slamming her she will turn around and let him know in no uncertain terms to back off. He gets the message every time. She gives him a louder and more intense growl than a playful one and she will kind of snap at him without making contact. But it's obvious to Oz, that she means get out of my face and leave me alone. She has never hurt him and he leaves her alone every time when she gives off that message.

I agree with the last post. dogs tend to sort it out themselves. Our two are very playful but sometimes Charlie does not want to play so Sam will lick his face, lick in his ears(which my husband cant look at ha ha), bite his leg!! and growl at him wagging his tail, but if he is annoying him charlie will snap at him once and sam knows to back off. He never makes contact, he just snaps and sam jumps back.

I asked this very question of our trainer when we got Shelby. I couldn't tell if Jake was tired of Shelby's play or not. She said to hold back Shelby....if Jake walked away he was done, if he stayed for more, he was okay.