I love a variety, so most tins I buy are opened and immediately jarred in Mason jars...which are then kept in a cabinet and sampled as I feel like it. Tins that I buy specifically to age, I just stash away until I need them.
I’ve got jars that have been going on for 12+ years as far as I can figure (it took me a few years to start putting dates on them...) and they’re absolutely fine-even better for aging in the jars in most cases, although a few have dried out a little probably due to not paying attention to the seal.
I used to leave the tobacco in the tin, but invariably I’d find myself distracted and I’d forget it for...a week? Month? Year? In some cases, the tobacco was fine, but in others, it was dried to a crisp and had to be rehydrated, risking mold...so I learned to just jar it up as soon as the tin is opened, before I even have a smoke!