I too agree with most of the posts that it is up to the provider. In my business I consider "grandfather" rates to be just that and they I do not change them ...forever.......without letting the customer know in advance before I begin to work for them, just good business disclosure (changing this seems a good way to lose business for me). I do sometimes, however, offer discounts to "Regular/Frequent" high volume customers and consider this a different matter.
Take care and happy hobbying out there!!!