What does Ecclesiastes 12:3 mean?

When the time comes that the guards of the house start to tremble, and the strong men stoop over, and the women grinding grain slow down because there are so few left, and those looking out the windows can barely see anymore. Ecclesiastes 12:3 - Modern Text Bible

(The 'guards' and 'strong men' refer to arms and legs growing weak, the 'women grinding' to teeth wearing down, and 'windows' to failing eyesight—it's a poetic way of describing the aging body.)