While cold doesn't kill batteries it makes you notice when they're dying.
This is very true. What's nice is that you'll tend to notice this BEFORE leaving your house. The car has been sitting all night, slowly draining away to the security system and stuff. Early in the morning also seems to be the coldest part of the day, so it's least likely to start. Try to start the car. It won't start. Stranded, but stranded at home is better than stranded at Walmart.
Anyway, my point is that a battery able to start in the morning will probably also start after you've driven the car around and the engine is warmed up. If you could start the car and drive it to work, it likely won't die at work unless you left the interior lights on or something else that drains power.
ShawnD1... While it might be the case sometimes you might want to re-think it...?
Here's a picture I posted last year. It's the outside temperature display in my Corolla
It was -28C (-18F) and the car would cold start easily, and it was like that all winter. Whatever temperature it was, that Corolla would start.
Last week, that same car with the same engine and the same viscosity oil and a nice fresh (couple months old) battery would not start at -5C (+23F). Letting the car sit for 2 weeks kills the battery a lot more than the coldest day of winter.
I still like to keep that battery pack with me. I don't want to be stranded because of something silly like leaving the heated seat on when the car is not running.