After the divorce, many times the divorcees go for their individual marriage to other persons. This is not very uncommon. So after some time if they feel that second partner is worse than the earlier then they can again go for a divorce with the second partner and once it is granted then go back to the earlier relationship. For this to happen, both partners should agree. There is nothing wrong or illegal in it. There is no point in having a live in relationship because that would not give one a legal cover. In case of differences and conflicts, live in relationship would not yield any benefit to the offended person. So even if one is getting married to the same person after some years it is advisable to register it or do it in a conventional way by printing the marriage invitation card and calling people for a party etc so that there is a proof and people can vouch for this marriage in case of a second scuffle. In western countries people marry so many times but every time they keep the official records intact. They follow a process so that there is no dispute of property and alimony etc.
Knowledge is power.