Yes, I have also booked continuous stays at different reservation rates for each night, when the rates vary. Usually just inform them at check-in that I've extended the stay and they combine the two reservations. Once or twice, I've had to check-out and check back in again, but always kept the same room. I agree that it is most annoying the website tries to charge the higher rate for the whole stay instead of varying the rates to the individual nights, which we know can be done.