Reflections on Sonnet 73

An old college friend emailed me and a few other classmates two days ago that he'd memorized Shakespeare's Sonnet 18 and recited it to his wife on Valentine's Day. That's the one you'll all remember when I tell you it begins, "Shall I compare thee to a summer day? / Thou art more lovely and more temperate."
    Less well-known is Sonnet 73. Its subject matter (aging) doesn't lend itself to assigned reading by high school students! It came up in the discussion after we had analyzed Sonnet 18 for a bit. Another classmate mentioned that his next book, whose subtitle will begin, "Growing Old...," will quote the sonnet:

That time of year thou mayst in me behold
When yellow leaves, or none, or few, do hang
Upon those boughs which shake against the cold,
Bare ruin'd choirs, where late the sweet birds sang.
In me thou seest the twilight of such day
As after sunset fadeth in the west,
Which by and by black night doth take away,
Death's second self, that seals up all in rest.
In me thou see'st the glowing of such fire
That on the ashes of his youth doth lie,
As the death-bed whereon it must expire
Consumed with that which it was nourish'd by.
      This thou perceivest, which makes thy love more strong,
      To love that well which thou must leave ere long.

To me the most touching thing about Sonnet 73 isn't the aging, but the effect on us of the aging of our loved ones. The poem's statement of this is all the more forceful for being located in its final two lines:

This thou perceivest, which makes thy love more strong,
To love that well which thou must leave ere long.

The statement certainly reflects what I myself feel as my wife and others whom I "love well" grow old. I love her and them more because they (or I) "must leave ere long."
    In fact, I've experienced the same thing with loved ones already dead; my love for them, too, has grown "more strong"—my love for my father, who died thirty-one years ago, and for my mother, who died six years ago. Whatever love I may have felt for my parents when they still lived, it could not have been so strong as the love I feel for them today.
    The sense of love's growing stronger over the years is so remarkable, I can't but believe that for Shakespeare, too, the sonnet was mostly about those final two lines.
_______________
Note: the Wikipedia article on Sonnet 73 (linked to above) says of the ending couplet: "Shakespeare informs his audience that we must 'love more strongly,' because in the end, we are going to leave it all beyond and respond to death." This interpretation makes nonsense of the fact of love's growing "more strong," which it does naturally and not because we obey some commandment to love more strongly.