Condensing meridians is indeed a marker for advancing to Grain Avoidance Stage, but the number of meridians one can condense is the crucial determinant of future achievements. Because the process of condensing meridians for a monk is a singular opportunity in one's lifetime. Once the meridians have solidified and the cultivator still wants to condense more, unless they possess some extraordinary heavenly treasure or opportunity, it would be impossible to achieve.
The number of meridians eventually condensed primarily depends on the amount of Mana within the body and whether they can timely draw spiritual power from Heaven and Earth during the condensation process. Of course, it would be best if there are appropriate Elixirs to supplement, the previous two naturally relate to the Skills practised and one's innate talent.