Yes, you can trim your braids, or make them longer after installing them, but it will be challenging. When cutting your braids, you'll need to do it individually to each braid, thin out the end, and rebraid it. In the end, you'll need to secure them with boiled water. If you need to add length, it is even more complicated, as you'll need to unbraid a bit, and add small pieces of hair extensions, so you won't see where it was added.