True, but can't we at least try to address the likelihood of that being the case. For instance, if we were living on a 9 Billion year old planet but we could o

True, but can't we at least try to address the likelihood of that being the case. For instance, if we were living on a 9 Billion year old planet but we could only find fossils dating back to 2 Billion years ago, we'd surmise that it took life around 7B to get life started on this planet. Under those circumstances, your hypothesis would be stronger than it is under actual conditions (4.5B and 3.5B respectively).