I flew from Brisbane to Perth last year; but it was in a
GOANA tour and even though we did not fly in company, it was good to know that there were at all times other aircraft aware of our general whereabouts. I would not have felt very comfortable doing the trip on my own.
We can give you some general feedback, but really you need to have a chat with the CFI at the flying school. Perhaps they are just 'milking' you for extra money, but it could be that there are very valid reasons why they want an extended checkout. You can probably size up their honesty fairly accurately; and if you're still unsure, check with some other local schools and see what their requirements are.