Well, we all want to start as soon as possible, but it will cause some changes that are irreversible, so it's best to be as sure as possible that this is what you want, truly, for the rest of your life. I'm not saying you have to wait, or how long you should wait for, but just make sure that it's a decision you're not going to regret. Some people know straight away, and some people need some time to figure it out, and if you know it's the right choice for you straight away, then it's not too soon.