Sarah (Stearns)Lathe(or Leathe) of Grafton MA

Sarah Stearns is one of my persistent dead ends. The vital record of her 6 Dec 1770 marriage lists her as from Worcester MA. Based on her death date and age at death, she was born 17 Mar 1750. Some of the data from internet sources says she is the child of Experience Bigelow and John Stearns.(He was a blacksmith in Worcester.) However I find this hard to believe since Experience was born in 1695 and a 55 year old mother in 1750 is improbable. Any suggestions?? Thanks.