The lemmings problem can be rectified by using the Carter reasoning on the number that will likely yet live, rather than on the time the species will remain. The time always requires further reasoning, but the number comes right from the probability analysis. But I reiterate, knowing what we know about species here on Earth, it would be silly to not try and do better than the estimate that comes from the Carter reasoning from zero information (which goes back to Fram's initial post).