If you open a jar you don't lose the accrued aging, but as has been said, aging starts over. I
never open a jar until I'm ready to smoke its contents. If you taste test a jar that has been aging for X amount of time and hasn't been opened with a jar that has, I think you'll find a significant difference.
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From Stanley Kubrick's "Dr. Strangelove Or: How I Learned to Stop Worrying and Love the Bomb"
"Mandrake, I enjoy the company of women but do deny them my essence."
Mike