That is not how common-law marriage works. It is not a function of how long you have lived together. You can live together for one night and be common-law married, but you can also live together for forty years and not be. What matters is that you live together as man and wife for any length of time, and that you hold yourselves out as a married couple. And you have to be living in a state that allows it, and only a handful do (bear in mind that if you are common-law married in a state that allows it, other states will recognize that marriage as valid).