I’ve had them corroded ones before they were opened for the first time. No signs of corrosion on the outside at all, but inside rusty as a old beached ship. Brunswick, Burgundy, Princes and Best Dark are all trouble makers for those tins. The reason F&T is in an awkward tube shape is to reduce surface area of snuff to air exposure. They aren’t really designed to be pinched from. They are not immune from corrosion though.
I have my Brunswick in a 100g crock that fits a sponge in the lid that cinches shut with a plastic seal. I don’t have very much in there but it likes the air. Some dry old Princes got tossed in never to be seen again. I like the Brunswick in the mornings. The citron is enough to get it in me to fill nose and the geranium pisses me off so much that I am up and adam ready to rip a chicken’s head off for breakfast,
Favoring the WoS Best Dark over the Brunswick lately. As for the tin degradation, don’t care about the “whys” and “wherefores”, it surely does occur! As noted by Xander and others, the tins of of both Best Dark and Brunswick I’ve received recently were seriously corroded. Immediately decant to plastic smashbox and all is good. Hmmmm… ripping chicken heads eh? Good Snuff!! (-;
I love Brunswick too. But I use a snuff box for my snuff, and never in my entire life bought a tin-tin for snuff! In my Icelandic silver box, it sits perfectly and fresh for at least a week or more. I have kept a W&S one pound container of Brunswick for a couple of years, and it’s still perfect 
Thanks to Whalen, I was fortunate to be able to try Brunswick, and have since fallen in love with the darker, moist snuffs. I absolutely love the aroma of Brunswick…it’s got a wonderful citrus aroma to me.