I haven't tried it yet, but the script by Altaris Greyhawke that you linked to should work.
Just copy the part between
Code:
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;; MODIFIED AGING CODE
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
and
Code:
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;; END MODIFIED AGING CODE
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
and place it in the campaign_script.txt file of the campaign you want to change. Make sure you put it right before the 2 final lines that say "
Code:
wait_monitors
end_script
Note that this script seems to cause problems with devastation when an army is in enemy territory. But personally I don't mind this problem much, as long as the characters age correctly