30000 hours seems like a lot, more than enough time for anything you might want to do. More than that, there might be enough changes in technology and the world that something you learn in the first 100 hours might not matter in the last 100 hours etc. If you start taking all these complexities into account, it might be better to count at a granularity of weeks rather than hours. Or maybe even ignore time, and focus on goals and aims. You can always make more or less time to fit your goals.