Ignore the expiration date on your toilet paper packaging. It can last a lot longer than they say. Years longer potentially. However, that isn’t to say that it will never expire. If the bag is left open it can get musty and mildew develops. If it is closed well, it will still eventually expire in the sense that it will lose its strength and be worthless. This takes many years though so unless you are a prepper that has a stockpile for the next decade, you don’t have to worry about your toilet paper expiring if you keep it closed tightly.