The long-term goal of a data scientist should be to become a subject matter expert in a particular field of data science (be it machine learning, or predictive modelling etc). This would ensure that the individual has sufficient knowledge and skillsets to manage all aspects of data science projects; however, if certain high calibre projects come up in a particular niche field of data science; the individual has the necessary credentials to support those high-visible projects.
This would in turn make the individual indispensable for the organization, and the same would have a positive impact on the earnings of the individual as well.
Although definition varies over individual and company policy, I think, becoming one ‘Data Scientist’ itself is a long term goal. Once you’re eligible to get the status of ‘Data Scientist’, you’d be the go to guy for any data related or implementation related issue. Of course the learning curve never stops even for a Data Scientist, and you’d encounter or tend to solve more complex problem, but people usually end up being a proper Data Scientist in this field.
If you’re already one experienced Data Scientist, I probably have not much to say, you’ve done your math.
If you’re a somewhere between a starter or midway through in data driven journey, I personally believe below pathway to set goal.
Data Analyst → Senior Data Analyst → Consultant → Data Scientist.
Add 5 years for transitioning into next step and you’d get the approximate of time and goal you need to set in order to end up somewhere.