By definition, a product with MaxValidDays should be able to be extended any number of times, even if the total validity period exceeds the MaxValidDays. This is expected since with each extension the product has to be approved again.
If such an order is extended, where the NEW ValidUntilProlongation is within the allowed period (calculated from <today>), but calculated from the original ValidFrom exceeds the MaxValidDays, an unwarranted error occurs:
 Value 'ValidUntilProlongation' must be less than '2/13/2021 12:59:59 AM'.
This this related to CR Number 33410 and CR 24334 - it was once specified there that a product can be extended any number of times despite MaxValidDays.