[Smushman]

Answer: Retirement. Kind of kidding - kind of not! Some will be thinking this though...

Jokes aside - it can be tough. I recommend if you have not already done a reverse time based analysis, you do so. If you're wondering this at 40, what about 60? Think about where you want to be and how you will be perceived going forward, combined. That will help guide some of what you do with an eye towards your longevity.

Anyway, at 40 there is a high expectation to support and mentor - first and foremost. Help people see their bugs, secondarily improve their methods, and thirdly listen to their ideas to help you paint their strategy (rather than your own interpretations and strategies which may be dated).

Second, younger people may see you as the older guy with the stodgy ideas. Avoid fighting with them on that front, even though your role may ask for that. You are in a losing battle often with that up front, unless your upper management really supports your ideas. And even then be careful to be respectful - you may change your mind after some research and find you support their initially backward sounding idea.

I recommend supporting and contributing to your coworkers projects to highlight your solution methods, and show them you care. You probably have a lot of good to offer, and this will defray any potential hostility.