re: Would you be ok with 21 being the law, with Military exempt.

There's really nothing magical about any age. 18, 21, 25, or 35.

I've read that the human brain doesn't fully mature until age 25.

The military wants 18 year olds because they're more willing to risk their lives thinking they're invulnerable. Older folks are a bit less careless. (This is why auto insurance rates go down when drivers hit 25)

I like the way it was in Wisconsin when I grew up. 16 to drive, 18 to drink beer, 21 to drink hard liquor and vote. A gradual increase in responsibility and freedom.