Do yourself a favor and buy a few appropriately sized Mason or Ball Jars, they will keep the contents of your tobacco as fresh as the day you placed it in them and will maintain it that way beyond all of our lifetimes.
Screw top jars are most likely the best, I use them. However I have a number of snap/lever type containers (ceramic) and they have held the tobacco fresh for over 5 years at this point. I guess it is up to you which is best.
I only keep 3-4 pouches open in my rotation, before I replaced the contents in jars, today I don't bother doing so because if I'm smoking them within 2-3 weeks maximum, I've found contents are still fresh regardless where I keep them,but if I'm buying tinned tobacco,then I always Jar contents immediately after opening(Flakes exclude- those go into Jars also but only after some couple of days.
OK, I've know done the aforementioned test off using essential oils and see if they escape in order to see if a seal is airtight or not.
The transparent seals on the flip top lids were the problem. I think they are made from silicone but I could be wrong.
Aroma, and therefore air (and probably moisture), escapes from them anyway.
When I changed seals to white rubber seals no aroma escapes.