Maybe I am unusual.
I do not know of ‘milestones’.
I have carried in one form or another for over 35 years, not always every day as you can not carry in federal buildings, but it was the federal government that sent me to become an armorer on both US and foreign firearms, and the S & W Academy, plus range time, and munitions and more……
Before that, often had a rifle or shotgun, even in the rack in the back window of the truck, even as a teenager.
Father was a Marine Drill Instructor and was taught firearms back in the 60s as a kid.
Was never bothered about carrying, open or concealed, but then I have a hard head and do not always care what others think.
Really can not think of actually meeting any milestones, unless I simply took them for granted and never noticed.
Oh… just thought of something… perhaps a milestone. I learned on revolvers and semi automatic firearms, 1911, Browning Hi-Power, TT-33, and others… the new polymer firearms I did not trust, and we even laughed at the Glock back in the early 80s… but the last laugh is on us (me and those I worked with at the time)… we spent so much time at the range, we just knew the Glock would fail, plastic gun that it was… milestone… accepting polymer firearms.