Retiring at 45, I wish

I always wonder when is the right time to shift gears and change careers.
I have personally made moves to many employers, owing to job satisfaction (10 till date). Obviously they gained from "one mans loss is others gain" theory. Even worked in the USA for around 5+ years, and a long career with a single employer. Now (I am in IT for the last 18 years), is it worth to switch to writing and research? (follow your heart where it takes?). Retire at 45 has been my goal (with passive investments), now I am 40 and 5 more years to go! You dont know whether you have done the right thing, unless you interact with others and understand and learn from their sucess!

Note - anyone with solid planning ideas, drop in a mail