It's sad to hear about your loss. Hopefully, the service can give you and your family a chance to celebrate their love and lives.
Regarding love, I don't think a love lost or a love that doesn't conquer all is any less love than one that spans decades. Love can be fleeting but very important at the time nontheless. I mean, the first love very rarely lasts but who can deny its overwhelming power? Some people are in your life for a while, then life changes. People change. We move on. But the love was still love. Maybe Rustle is right. It only metamorphoses.
Then again, having someone in your life for a very long time is undeniably an amazing experience. I've been with my partner for over 20 years and the thought of us breaking up is almost unthinkable. But we would survive. And our life together would still have been amazing. Our love just as true.
Just some rambling thoughts...