Being 40 shouldn't be an issue, however there are a few things to keep asking yourself to stay relevant on the way:
-- What is your goal?
If you don't know where you're going, the chances are your career trajectory could be plateauing, or even going backwards.
-- Are you progressing?
Pick a metric aligned with your goal and then measure yourself against it (e.g what you can measure, you can manage). Whether its specializing technically or moving vertically into management, its really important to keep moving in that direction, and to ensure that you are "compounding" your skills and successes along the way.
-- Are your skills transferable?
At all costs, ensure your skills are transferable. This will give you endless options and freedom to take breaks and move companies at will. NEVER allow yourself be the highly paid person on an obsolete project/system, not even for a year.
-- What is your goal?
If you don't know where you're going, the chances are your career trajectory could be plateauing, or even going backwards.
-- Are you progressing?
Pick a metric aligned with your goal and then measure yourself against it (e.g what you can measure, you can manage). Whether its specializing technically or moving vertically into management, its really important to keep moving in that direction, and to ensure that you are "compounding" your skills and successes along the way.
-- Are your skills transferable?
At all costs, ensure your skills are transferable. This will give you endless options and freedom to take breaks and move companies at will. NEVER allow yourself be the highly paid person on an obsolete project/system, not even for a year.