When do they calm down? I don't know, I'm still waiting with my 6yr old, 3 yr old, and 6mth old, LOL
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No really, they do calm a bit after the first year or so (in my experience)...and then you see some other parts of their personality emerge, which is fun (little quirks). But, my furs also have a ton energy and are ready to play at any time - just say the word.