Not advertising it is key. I'm also coming up on 50, and people constantly are surprised when they inevitably find out how old I am. Ageism can unconsciously creep in when you have more than 15 years of experience visible on your resume, even for higher management-level positions.
Also - if you're a mid-level IC in your 40's you should start asking yourself what's stopping you from being higher up on the IC or management tracks. "Career senior engineer" is not a great place to be, long-term.
Also - if you're a mid-level IC in your 40's you should start asking yourself what's stopping you from being higher up on the IC or management tracks. "Career senior engineer" is not a great place to be, long-term.