I have lots of snuffs which are older than 4 years already and they are perfect, maybe even better than when I got them. Glass jars, airtight, cool storage are the main things to remember.
I bought cobalt blue jars they look & work great 4 ounce Jars for my snuff and 8 ounce for my pipe tobacco cellar.
When ever I open one to fill a box I just breath a little hot air into the jar just before sealing the lid.
Always as moist and fresh as the day I popped open the tin
I figure they will be around for a long time and my grand kids can sell them to pay for college after I am dead.