When the default payment terms are changed in 'company details' have an option for it to update all existing customers default terms. This will save time as you will not need to click in to each individual customer to edit their terms. When creating a new customer the default will match what has been set in 'company details' rather than 28 days. If it is an option then it still means clients with different terms for different customers can opt in or out but will save a lot of time for those who need to change one blanket default.