If you click on the strippenkaart, immediately be able to see if it is expired. Now you have to click on ´change booking´ and in the list of bookings see if the card is expired. You don't see any difference now between a strippenkaart that is expired and one that can still be used. If possible, I would like to see an automatic mail sent an x number of days before the strippenkaart expires to let you know how long it is still valid and how many strips are left.