Elemental mercury is a shiny, silver-white metal that is a liquid at room temperature and is traditionally used in thermometers and some electrical switches. If not enclosed, at room temperature some of the metallic mercury will evaporate and form mercury vapours. Mercury vapours are colourless and odourless.
How much time need to pass for an AR account to be considered delinquent? The amount of time required to pass for an AR account to be  considered delinquent is 30 days.
There is no time limit on that debt. A collection agency can legally pursue you until the debt is paid in full.   However, there is a time limit on the negative consequences of not paying the debt. In most circumstances that limit is seven years. Seven years from the time you became delinquent with your original creditor.