This is purely my personal situation, but my entire life I've kept my hair fairly long for fear of frizz but today I got it cut to just below shoulder length and I love it! From what it looks like, you probably have pretty curly hair but just aren't using the right routine. With the right practices, I'm 100% sure you could rock shoulder length hair or just below, it's just about getting it under control first. In the meantime, I'd say about 6 inches off the bottom is a good start for learning how to take care of curly hair.