Charlie Morgan wrote:

But... why would you open the new one if there is still product left in the old
one,

To compare it to the old one. Come on, Charlie.


and you think it never deteriorates?

I never said I think it never deteriorates. I said I was skeptical
about the claim that it has an indefinite shelf life while on the
retailer's shelf, yet when the consumer takes it home and starts to use
it, it's only good for two years.