I use Tupperware to store/cellar my tobacco. All of a sudden I get second thoughts about it. Do you thing they will develop a plastic taste over time? Glass jars have rubber sealing too, haven't they...?
It's not the imparted flavor one way or another that you have to worry with concerning Tupperware, but the fact that it breathes. Your tobacco is not nearly as sealed air tight in Tupperware as it is with tempered glass jars.
Yeah, I'm thinking tupperware might be a problem. As tobacco ages, it might start to break down the plastic. You might not be able to see it, but it's happening. Now picture yourself lighting up a bowl of plastic-tinged anything.
Many years ago, I used a tupperware container to keep a few cigars. Not for decades, but from one month to the next, or even a couple of months. It was OK for short term and think that if you are keeping an opened tin in a tupperware container for a while to prevent the tobacco from drying out, it should be OK. For long term storage I'd stick with glass. Whether the seal on the mason jars is rubber or silicone, so little of it is exposed to the tobacco that it does not matter. If you want to avoid glass for some reason, some folks have good success with mylar bags for keeping tobacco.
Another agreement that while Tupperwear should not negatively impact flavor from the plastic standpoint, its not adequate for long term storage.
Mason Jars are the well accepted and proven solution to this. The silcone ring should not be in touch with any of the tobacco anyway.