I have a China pink that I have never pruned (although the horses did one year and I thought that plant was gone but it eventually came back) and is a few years old. I don't want it to get any bigger and am not sure when or how to prune it. Everytime I go to do it, it is flowering. We have frosts but should not get anymore now.
Loropetalum is easy and does well with pruning. Wait to trim it until after if finishes blooming in the spring.
Here is a link with more information.