i opened up my first big tin of MacBaren Vanilla Cream about a couple years before i actually started smoking from it often. it stayed the same over those couple of years.
i also had some ceramic jars that held my old cheapy B&M bulk aromatics. i cleaned them out last fall, and they had tobacco that was close to 7 yrs old still inside, smokeable even.
i've never had it happen, so i can't say for sure.
what blend was it, cuz maybe that's the flavor/aroma it's suppose to have.