I've encountered this a few times and have had good luck with a Hilton CSR making the reservation such that I benefit from the lower rates. That said, I was lectured once by someone at the Diamond Desk telling me that agent shouldn't have done that. My reply was something to the effect that if that agent hadn't done that, the Hilton property would not have got my business on that trip. So I think they acted properly.

It galls me that a customer, that stays more nights should be "penalized" with a higher rate just because they check in a day or two early. Quite the opposite of a quantity discount.