At what age is it a woman's giving birth not noteworthy as a miracle?

The RALBAG shares the Ibn Ezra incredulity at Chazal's including Yocheved among the 70 souls who came down to Egypt. Even if she were, as Rashi records, born between the walls, she still would have had to have been at least 130 when she had Moshe, as we know that Bnai Yisrael were in Egypt for 210 years when Moshe came before Pharoah at the age of 80. Wouldn't Sarah's giving birth at 90 pale beside that feat? So these commentators observe it would be astounding for the Torah to not comment on such a great miracle. The RALBAG suggests that Chazal were making a non-literal point but that Yocheved was not at such an advanced age. According to his calculations, Yocheved could have been a mere 58 at the time of Moshe's birth if she were born to Levy at the end of his lifetime. Giving birth at such an age is not so remarkable (especially given lifespans greater than 120 years).

Another observation of the RALBAG made me think of Mother in Israel. When Miriam offers to get a wet nurse for the infant Pharoah's daughter has found, she gets his own mother. He says there that the very best source of nourishment for a baby is his own mother's milk. (no Similac here)