How old is too old?

The other day I watched my husband take tylenol that was passed it's expiry date. When I asked him about it he just shrugged it off. I told someone else about this they said they ignore the expiry dates on Tylenol as well. Apparently there is more than one person out there who doesn't care about expiry dates. This leads me to the question, how old is too old? Would you take tylenol that was a month old? 6 months old? a year? 10 years? If you aren't following the expiry day then where do you draw the line? And does this disregard of the expiry dates apply to all products? There are expiry dates on dairy, cereals, breads, meats, juice, medication, contact solutions, contacts, car seats, poison, and condoms. So I must ask again, how old is too old and do expiry dates apply to any of these products?