Mars in relationship compatibility never contributes to longevity of a relationship. It almost always deals with passion and action. Passion (more so in the sexual area) is always nice to have, but never contributes to an emotional tie. You see and hear stories all the time of people with heavy Mars related aspects, and a lot of times, the people are drained by this energy, because it's so intense. Also, anything involving the Sun almost always is at its most powerful.....when it involves the moon or NN in some form or fashion. The Sun/Moon aspect is widely seen as a high compatibility aspect in relationship charts, as is Sun/NN.
This just just leads to my next argument...I would rather have Moon in aspect with someone else's NN. The NN denotes what you must do in this lifetime to be at your most happiest, most satisfied. It's something you NEED to do in order to grow spiritually. When someone's Moon comes in contact with someone's NN, that Moon person has what the NN needs EMOTIONALLY in order to actually grow on the inside. They are extremely beneficial to one other, it's way more long lasting, because the people involved feel like together, they can fulfill their deepest needs. Even if they were to part ways, a strong Moon/NN contact can make people actually still long for one another and be so fond of the memory of the other person. Usually when people break up, they don't really think about their ex anymore. I've read stories where people with strong Moon/NN aspects, years after breaking up and even with new people, a person will still fondly think about their ex....because the emotional connection never truly goes away.
Also, some astrologers out there believe strong NN ties are the secret ties that bind. People who have less than impressive synastry/composite with each other, will still share a strong bond if there is SIGNIFICANT nodal ties (more so NN ties, because it shows growth, rather than past lives of the SN). Because even if there isn't strong sexual chemistry, or they don't have a lot in common, the couple will likely still feel compelled to stay together anyway, because they are being fulfilled on a deeper level. This tends to involve the NN, because like I said, the NN involves what one must NEED in order to be happy in this lifetime, and to grow spiritually and be fulfilled. Someone's Moon in strong aspect to the NN fulfills this duty in satisfying the NN person, (and the Moon person tends to love doing this), that the connection is super strong.
A strong Moon/NN aspect also gives a sense of "fatedness" to the couple. They really feel they were meant to be together, and brought together by some higher working.
If there is a significant double whammy of Moon/NN....that's arguably the strongest pure emotional bond out there.