"Like sands through an hour glass, so are the days of our lives"
Haha, sorry! I just thought this was a little funny.
But I like the "Our love is timeless" one
What about what Carrie engraved on Big's Watch on SATC2. "Me & You, Just Us Two" although it doesn't really have anything to do with time and they didn't want kids, I still thought it was so cute!