A famous Maggid once emphasized another point which underscores this important lesson. As we see, Sarah Imeinu worked tirelessly to achieve her life's goal, ensuring not to let even a moment go to waste. Thus, hundreds of years later she was rewarded that her great granddaughter Esther Hamalkah ruled over one hundred and twenty-seven countries.
However, it wasn't merely a country for each year of Sarah's life. Rather, each moment she utilized properly granted Esther sovereignty over another area; each hour Sarah used well granted Esther rulership over another village. Thus, Sarah Imeinu was rewarded not only for her life as a whole, but for every moment she utilized properly.
Hence, Rabbi Akivah used this specific idea to awaken his audience, being that it highlights the value of each moment and the great importance of utilising it in order to grow in Avodas Hashem.
(See נזר הקודש on the Midrash at the beginning of this week's parshah)