When we left for Melbourne, it was actually earlier than we'd planned; but that was purely because we had been packing all night, so when the kids woke up we figured there was no point in delaying:-)
What advantage we gained by leaving early was _more_ than off-set by the software error that caused us to hang around in Midland until we could find a mechanic to check it out (and then for us to snooze in Northam, because _neither_ of us was fit to drive:-( )