Casper and Kitty are soon 12 months, and I'd say for the past month they haven't grown at all...In december our vet said they woulnd't grow anymore, but after that, Casper took a spring and grew (taller). Casper is pretty long now too... I'm not sure when they actually stop growing...Ours seem to have stopped that now (and they will probably start growing the other way now, side ways)