The larger cans spray for 10-20 seconds, which, coincidently, is the same amount of time you are shitting your pants as the bears comes towards you.
Sounds perfect for survival: You can spend the next couple hours cleaning your eyes of spray and your drawers of excrement. That's super easy to do with a handful of dirt & some leaves. I wonder if its warm enough to go for a swim around the island? They wouldn't stick them out there in the winter, that would be a lawsuit waiting to happen.