Stress is actually related to your work environment rather than the busyness of your job. Your stress may come from unrealistic expectation and this is why you feel stressful even working at home.
I always decline any offer of working at home. Home belongs to my life and my house is my castle.
The problem is that when you are approaching 40 and you are still a developer you feel the job is boring. However, it's hard to bargain more pay rise since at the end of the day pay level is decided by the market rate.
Nothing is too late and the age of 40 is quite young :) My two cents.
