One of the biggest factors in bringing up young players from the minor leagues is when they have done all they can do down on the farm.
A young player who dominates his minor league-level over a couple-month period should be promoted to the next level. A player who dominates Triple A over a long period should also be promoted.
No matter who is in the major leagues in front of him.
No reason to keep a young pitcher in Triple-A "for more seasoning" when he has filled up every spice rack in the country.