How many years needed to become a good rates trader?

This is kind of a silly question, but I'll try cause it might be useful for others. The answer: it depends.

Many people never get there, either due to intellectual inability, lack of work ethic, lack of quality mentors, or being at the wrong place at the wrong time. 

For those with the necessary primordial ingredients (the above), I'd say the following is a reasonable track:

• 6 months - 1 year: learn the basics, after this you can at least understand what people are saying
• 1-2 years: master the basics, start to have some initial original market views/thoughts, though perhaps not very polished. Put on a few small positions.
• 2-5 years: at this point things start to diverge wildly, largely due to difference in innate ability coupled with opportunity set and mentor quality. Some people continue accelerating and go onto kill it from here. Others continue to learn, albeit at a slower rate and chug slowly upwards. If you're good, you'll start to have more sophisticated and nuanced market views, trading several themes and having multiple expressions of the same theme.

In general, I'd think of learning, as it pertains to markets, in terms of 2-year half-lives, each of which have their own learning curve that looks like logistic growth. So, you'll start out knowing nothing and bang your head against the wall. Then you hit an exponential portion and learn a bunch. Then, as you master the basics you hit a plateau again, but this time with more knowledge. Rinse and repeat as you learn new skills and markets.