Hi from 47 y.o. and also not on the management track (any longer, BTDT, FT)
I only list the last 8-10 years of stuff on my CV. Not specifically to combat ageism (I keep a "full" version also -- 6 friggin pages these days) -- but mostly to acknowledge that just because I did something cool 20 years ago, doesn't mean I am current, fluent, or even looking to do that again -- so why bother? If anyone cares, they'll ask and I'll answer.
My full CV is basically buzzword bingo at this point, and is spanish fly to the body-shop recruiters who love to email, text, and call me with just the worst jobs ever. :) Keep that thing offline unless you like to stay abreast of junior QA analyst jobs in West Virginia for $27/hr.