 While there is no specified expiry date of such a qualification the changes in legislation it is suggested to update every five years.Best before indicates a future date beyond which the food product "may" lose quality in terms of taste or texture amongst others, but does not imply any serious health problems if food is consumed beyond this date (within reasonable limits).Use by indicates a legal date beyond which it is not permissible to sell a food product (usually one that deteriorates fairly rapidly after production) due to the potential serious nature of consumption of pathogens.