Not so much an issue all the time, but I always carefully check the rim of the jar as well as the lid. Sometimes small bits of 'baccy will get compressed on the rim, ruining the seal. Other than that, if it seals I can usually tell. I tend to take the leaf that I am using every few days out of the jars and load my pipe pouches - one with English, one with Va / VaPer blends. Aros I just leave in ziploc bags since they usually don't have drying issues.

Now what to prep for tomorrow morning....thinking either a rope or a plug.