How long a goal takes to achieve has a lot of variable factors that, without a lot of background in the sorts of things you are fixing to do, it is hard to be tremendously specific. How old you are might be a limiter. For instance, if you are seven years old, and want to pilot space shuttles, your goal cannot be achieved until you get out of school. They probably won't let you pilot a shuttle until you have passed your 18th birthday.
Start working toward your goals right away. Your career, anybody's career, is a historical document of all the things they did. When people say they are concerned about whether their (current) course of action matches the story they want people to have about them. I have had several distinct careers, and they have been in general areas that were interesting to me. I made sure my social media was synchronized with the person I wanted to be known as. Your written voice in social media will follow you through your entire life, so resist the impulse to be impulsive and show risqué partying pictures anywhere.
I think every time you set the goal, you can also set a date to review how far you go, which can reflect what you have done in that period of time. And then you can improve your action everytime after the review. Before you set your goal, you need to consider if the goal is achievable, specific enough, measurable or not. Then, set some short-term goal in order to achieve or support your long-term goal.
For example, short-term goal will take around 3 months. Long-term goal will usually take around 1~3 years.
Hope this help.