Brand new? Check the dates.
 

In March, 1994, we bought the boat. Later that year or perhaps the
following year we bouight a Lifesling with battery-operated strobe light.
Brand new. That battery has a long shelf life and we never thought to
check it. Yesterday doing some mainteance on the Lifesling and its
container I pulled the battery out for a look.

It had dates on it. Manufactured in February 1989 and to be replaced in
February 1994. The battery was already stale-dated at the time we bought
it as brand new.

Moral: If you are buying anything with a battery in it, check the battery
before you leave the store.