We plan on visiting both sites on Friday, June 29th. Can anyone tell me if it is necessary to purchase the tickets in advance? It is a $2 per ticket charge for each house and since we have 4 people, this really adds up to the equivalent of purchasing an extra ticket. Also, with the ATO, it is necessary to select times for each house and there are no refunds. How much time should be allowed to visit each place? Although I would rather buy tickets on site, I also don't want to arrive to find out all the tickets are sold out. Any feedback is appreciated.