Technically, when all rat lines are routed, a board is done. However, it is important to run rule checks. In fact, it is better to run rule checks as a board is being routed. Rule check ensures that no production rule is violated.
You should set up the rules as soon as you have decided which fabricators will manufacture the PCB. Different fabricators have different manufacturing tolerances. For example, some fabricators can manufacture traces as thin as 7mil (a mil is a thousandth of an inch), while others insist on a minimum width of 8mil.