Newbie downunder

Hi I was wondering if anybody knows of any set rules regarding how much money is put on hold during a stay and when it should be credited back to your credit card? I recently stayed at the IC Melbourne on a reward stay and asked how they worked out what to put on hold. I was told it was the the nightly rate paid multiplied by the number of nights plus $100 AUD per night. As this was a reward night, it was charged at $79.95 AUD per night (I am assuming this is what PCR is charged by the hotel for the reward stay) as it is normally approx $200 AUD+ per night. It is the second time they have done that 2 me in the last couple of weeks. Last stay was 2 nights at $220 p/n + $100 p/n totaling $640. It seems to be a very expensive authorization and they are very slow at crediting it back to my credit card. The hotel told me it should be back in my account in 5 -7 days. I really think that is not good enough so I rang my bank and got them to reverse it as they agreed it was ridiculous to hold onto it so long after checkout. Any suggestions?

Cheers