I am never far from a back up so I never carry anything with me. If anything goes amiss I always have access to a medical professional (spend more time around these folks than my family) who is willing to give me a little pull off the old vial in the back alley and/or my house is within easy range.
I tend to be able to go a good 6 hours or so before I even begin to burn much ketone for energy. If we were dealing with AR's scenario of weirdo's holding up places of employment then if the weirdo is still around at 6 hours after pump malfunction then I will be bum rushing him with AR. Two PWD who NEED their insulin? Weirdo won't stand a chance!
I'm on the pump and carry at least a few scrynges with me. When I had upgraded my pump, I actually had kept my pump and use it as a backup when I need to. Since insurance took care of the whole thing but $75, I thought in keeping it just in case. Even though Medtronic is good at getting a pump out to you next day delivery. I had just wanted to make sure I had one stuffed away.
Every time a change is made on the pump, I backup the settings on the computer and print out the settings and put them in my carry bag.