If you are wondering if the jars are sealed, then take the ring off and check to see if the lid comes off easily, or turn it upside down and shake it. If the tobacco comes out, it never set.
The brass ring that holds the lid on, is designed to merely hold it in place. No matter how tightly you crank it down, it will not make the jar lid tighter. So, if the tobacco doesn't use up the oxygen and seal the lid, it's never going to seal.
The ring is designed to merely hold the lid in place while under the mild pressure of a pressure cooker, which allows the air to escape easily. In instances of canning green beans accidentally under too much pressure, I have had all of the beans in a jar shoot out from under the lid and ring, leaving the beans floating in the cooker with the jars empty but the rings and lids undisturbed. It was like a weird magic trick.
That said, if a tiny bit of tobacco comes between the jar and lid, or the lid just never sets, or the tobacco just never starts eating up the oxygen as it ages, the lid will not set. Also, extreme fluctuations in temperature or pressure will unset a lid also.
I take the rings off of mine after they set, to make sure the lids all stay set. I can easily check by turning the jar upside down and shaking them.
Once sealed, the lids should stay sealed. I have never heard of a seal failing because of age.