We did the Great Ocean Road tour, and it was, indeed, a very, very long day. If you have access to any ocean road trips, such as in California, I wouldn’t spend time on this one. The Great Ocean Road was constructed as a tourist draw years ago, which we didn’t know, and the twelve apostles are rather reduced in number at this point. We wished we had done the fairy penguins instead.
What we very much recommend is the Echidna tour where you travel into the country to see koalas in a natural preserve and gangs of kangaroos in another preserve. You walk around the woods and the guides show you the animals. We saw quite a few koalas and an amazing gang of kangaroos, one nursing and with a baby in it’s pouch. The dominant males were enormous and very much worth seeing. They also give you billabong tea and local food. All in all, it was one of our favorite parts of the trip, especially since you don’t see any animals in the wild otherwise.
Good luck with your choice.