I know I should, but I don't.
I do have a couple of loaded mags in the console of my truck and a couple more here by my computer.
I work in a gun store where you can usually find three of the four employees at any given time.
The owner carries a Commander size Colt 1911 on his hip and a Kel-Tec .380 in his pocket as backup.
One employee carries a Springfield XD-45.
One employee carries a Browning Hi Power.
I carry a Smith & Wesson Sigma SW40F (15+1 .40 S&W) and a little NAA Pug 5-shot mini-revolver in .22 Magnum in my pocket as a backup.
No one carries any spare mags (that I know of).
There's a loaded double-barrel shotgun under the register and a loaded AR15 in the owner's office.
Our shop is also a hangout where several retired LEOs (one of whom is a highly-regarded competitive shooter) sit and drink coffee and tell tall tales all day. I'd be surprised if they're unarmed.
I think it would take a lot of firepower to overwhelm the place.
Just saying that I don't believe the presence or absence of a spare 15-rd mag on my belt is going to make any real difference.
I should still have one. As has been mentioned, mag could fail. I've got the extra gun most of the time, but a palm sized .22Mag is not much of a replacement for a full-sized .40. Better than a sharp stick, I guess.
I'm downsizing (upgrading) to a more concealable Kimber Ultra CDP as soon as I can get it off layaway. I do have a spare mag pouch for that, which I intend to wear. With only 8 rounds in the Kimber, I want more ammo available; just a security blanket since I'm used to carrying 16 rounds in my current pistol.
From Tucker Gunleather I got The Answer IWB holster for the Kimber, an IWB spare mag pouch, and a belt. I've got the spare mags, some practice ammo, some JHPs . . . just no Kimber yet. Working on that.
