Totally agree with Atmasphere about tape storage. I have c-cassettes that are over 40 years old and most of them perform just fine. Furthermore I play cassettes in my car in hot summers and very cold winters (28 Celsius minus at lowest).
Certain cassettes are kept many years in my car but never in direct sunlight. Baked or frozen cassettes play nice to me. Of course, excessive heat ruins tape but not excessive cold, heh maybe make the sound more fresh ;-)
Cassettes never sound dull but I have had some worse quality tapes that soon lost higher frequences and become worthless.
Certain cassettes are kept many years in my car but never in direct sunlight. Baked or frozen cassettes play nice to me. Of course, excessive heat ruins tape but not excessive cold, heh maybe make the sound more fresh ;-)
Cassettes never sound dull but I have had some worse quality tapes that soon lost higher frequences and become worthless.