If they're ready then they're ready. My cousin adopted a shih tzu puppy last summer. Their other shih tzu died three years ago and my uncle was I guess missing the companionship (the shih tzu that died was a family dog but stuck to my uncle) so they got another shih tzu.

This new one, chloe, adorable as hell but evil. two weeks ago she farted by my uncle and when he yelled at her, she just turned around looking at him all innocent