This was the first email at 13:22 (I bolded the important point) :
This is a friendly reminder that your iStockphoto Pay-as-you-go credits will expire within 1 year of the date of purchase. Your Pay-as-you-go credits will expire in 15 days if not used.
Next at 16:26 :
… Your Pay-as-you-go credits will expire in 30 days if not used
Good news at 19:35 :
… Your Pay-as-you-go credits will expire in 60 days if not used.
And on a big roll at 22:27 :
… Your Pay-as-you-go credits will expire in 90 days if not used.