I think in any breed, each dog has a different personality. Of course some breeds are known to be more active then others.
However don't judge a book or dog by it's cover. We have two Schnauzers, terrier terrors, they are completely different. All day Daisy wants to play with her toys, play catch the ball, run through the house. I take her outside every day and throw the ball for her to give her more exercise, she can keep going and going.
On the other hand Perry is content to play for a little while, maybe run for the ball twice and give it up, play with his toys for a little while, but what he really loves to do is go in his crate and take naps or jump on my husband and give kisses and sit with him.
So I don't think so much it's the breed, but the personality of the dog.
I have to admit I don't know a thing about Bostons.
Jackie