I believe that it is never too late to start a new career or shift your careers. Whether you want to learn new things or you want to break your routine or you want more money or you want better life status, whatever the reason is the most important thing is to be courageous and dive in.
If you are thinking of shifting your career completely or retiring, give it a second thought & push yourself to try new things that might interest you more. Add to your basket instead of changing it!
To make it even smoother, you have to plan for your retirement ahead of time. Your career is all yours whether you shift it or add to it is all yours, so stop talking to people who might be negative. In addition to this, you have to experience new things all the time to keep your mind fresh through breaking your routine.
I personally have experienced something like this, after 2-years of my full-time job I have found that work is stressful & there is a fine line to balance between life & work however I can't find this line. So, I have decided to add to my basket. I have added philanthropy through volunteering with the Rotary & blogging through reviving this blog again & write in more regularly.
It is your call to add to your career or shift it! Personally I prefer adding to it to explore different backgrounds and know more about different things which will give you an edge over someone specialized in one thing only.