I will second the earlier cautions about buying batteries in quantity from Amazon. It certainly looks like a good deal, but in my experience the button batteries I've received have varied from fresh to quite aged, with a number of failures right out of the package (sometimes while the package itself literally fell apart). Others, while not tested immediately, didn't work when called to duty a few months later (though others did).
If you're only taking care of your own machine and not a bunch of them, it's best to get a battery fresh from an electronics shop (or even a watch shop, even though that's not a popular size for watches) and just consider it a one-off.