In what way is "The Nymph's Reply" an expression of the philosophy of tempus fugit, or "time flies"?

The philosophy of tempus fugit really begins to emerge in the third stanza of "The Nymph's Reply." In this stanza, the speaker (taking the character of the nymph who is being pursued) notes that "flowers do fade." This is a reflection upon that most beautiful moment in a plant's life cycle during which a flower emerges; however, this is short-lived, as all too quickly, the flower begins to lose its brilliance of color and then slowly succumbs to death.
This is symbolic of the shepherd's romantic pursuit. Even if a beautiful flower emerges from a love affair, the nymph says that it will be short-lived and is destined to fade and die. She notes that the shepherd's tongue made of "honey" (or his sweet words) is destined to lead to her sorrow eventually, just as spring turns into the decay (or sorrow) of fall. Tempus fugit.
Stanza four examines Marlow's promises made to the nymph in "The Passionate Shepherd"; the nymph notes that all of these things "soon break, soon wither, [and are] soon forgotten." Again, the idea of tempus fugit, time flies, is felt in the impermenance of the shepherd's vision.
The nymph concludes the poem with several things that quickly hasten by in life: youth, love, joy, and age. Life itself, and all that it consists of, is fleeting. Her conclusion is that if it were impossible to escape the tempus fugit constraints of life, she could possibly love him; however, her ultimate point is that this is an impossibility, as life quickly flies by us all.

The expression tempus fugit comes originally from a book by the Roman poet Virgil in which he wrote: "Fugit inreparabile tempus," or, "It escapes, irretrievable time." We usually translate tempus fugit from the Latin as "time flies." It could also be translated as "time escapes." In other words, time continues to move ahead; it never stands still.
"The Nymph's Reply to the Shepherd" by Sir Walter Raleigh is a companion poem to "The Passionate Shepherd to His Love." In "The Passionate Shepherd to His Love," the shepherd pleads with the nymph to "come live with me and be my love." He offers her adornments such as beds of roses and posies, a cap of flowers, a gown (kirtle) embroidered with myrtle leaves, a gown of wool, slippers with buckles of gold, and an ornate belt.
The nymph's reply to the shepherd does express the idea of tempus fugit, for she tells him that all these things he has offered her are temporary and will pass away in the course of time. The gowns, the shoes, the cap, the beds of flowers, and all the other adornments eventually will break, whither, and become rotten. Because everything that he offers her will become worthless after the passage of time, his gifts do not inspire her to come to him and be his love. The last stanza implies that the things that would win her heart are everlasting love, joy, and youth.