Depends upon what you want.
I hasn't halted my trees from growing tall.

I topped one of mine and then trained it to curve.
But then Nature topped the other two in storms, and now all three of them lean to one side with that windswept distortion so typical in Japanese gardens. I love it. It just adds to the authentic Japanese look - like a tree might look after growing on the rocky side of a windswept mountain in Japan.

But, like I said, it all depends upon what you want it to look like in the years to come.
~Annie