A first marriage lasts at least 12 years on average. If a marital disagreement leads to divorce, there are several problems that a couple must overcome before the marriage is formally dissolved. The length of a second marriage varies depending upon how long the couple wants it to last. If one or both parties would prefer a shorter marriage, they can agree to such a situation. Otherwise, a second marriage will usually last 10 years or longer. A third marriage tends to last about as long as a second marriage, on average. A fourth marriage is also expected to last about 10 years. It is difficult to say what causes marriages to fail. However, if a marriage does collapse, it most likely won't be resolved quickly and may even result in divorce proceedings. A family law attorney should be consulted if issues arise during a marriage.