Whenever I replace my lifejacket I always test it prior to first use. I don't want to find out it's faulty when I am bobbing around in the freezing cold ocean.
So I opened up the jacket, removed the gas cylinder and auto firing capsule, and then inflated it with my foot pump
Over 12 hours later and it's still inflated
Then it's time to deflate, refit the gas cylinder and auto firing capsule, and repack the jacket