One of the many meanings of the Lovers is indeed the state of being in love of a new couple. But the main aspect of the card's meaning is best described as the love of a couple who live with each other from the time of their comming together until their death, full of respect and loving care for each other. This is the love of two people who have decided to choose each other, and who have the will and the strength to keep to this choice even in difficult times. So this cards essentially stands for the full-hearted decision, for the unconditional "Yes". In many cases this will indeed be the Yes to a romantic relationship, but it could also be the Yes to a child, to more responsibility in your job, to a spiritual path, to a house you want to buy... But always it is a Yes that implies the willingness to take responsibility for that which you have said "yes" to, the willingness to treat it with care and mindfulness, to protect it - to treat it with love. And all this means (at least where a relationship is concerned) that you fullheartedly agree to do this forever.
See also the annakblogs article >> What's the difference between the Lenormand card Heart and the Tarot card The Lovers?