Films now have much shorter expiry dates than 20 or 30 years ago, so does food and many other items, it's part of ISO 9002 compliance. So expiry dates are now quite short a few years less then when I took up photography but the films still behave perfectly for years past the modern expiry dates.

I've made some great images on short dated HP5 bought from the US and marked short dated on the box well after the expiry date (4 or 5 years), in fact I still use some innthe UK and the results are no different to newer HP5 film I've used in Turkey.

Ian