...PS

Many people enter relationships for many reasons. Because they're lonely, because their friends have them, because it's expected, because it seems right, because they want to, and sometimes because of love. Whether this love be of a romantic, platonic or passionate nature, I think it's fair to say that feelings have been known to change. What may start out as platonic love may slide into passion, romantic love may fizzle into friendship.

So what was Shakespeare thinking when he wrote his sonnet number 116?
(...) Love is not love
Which alters when it alteration finds,
Or bends with the remover to remove:
O, no! it is an ever-fixed mark,
That looks on tempests, and is never shaken,
It is the star to every wandering bark,
Whose worth's unknown, although his height be taken.
Love's not Time's fool, though rosy lips and cheeks
Within his bending sickle's compass come;
Love alters not with his brief hours and weeks,
But bears it out even to the edge of doom.
If this be error, and upon me proved,
I never writ, nor no man ever loved.

Spur of the moment, realistically speaking. Or are we really meant to believe Billy felt like this (for the same woman, mind) until he died? Be that as it may - who cares? I mean, who am I to judge? And would it really be such an enviable situation if the love remained romantic like in those first few months, without evolving? The main thing should be that he felt this way at least at one point, right?
The longevity of that particular love will have depended then as it does now, on the continuous commitment of the two partners to themselves, their values and their future plans. Show me a relationship that is working without even the slightest glitch and I'll show you two people in denial.