usually a small dog such as yorkies, etc. slow weigh down around 6 mos. they may put on another lb. or so, but, the vets I've used have both told me around the 6 mo pt..of course, sometimes they surprise us and keep growing and growing like my first one did..
She was around 7 lbs at a year, and is now going on 5 years and 14 lbs.