You want to be at a Major by age 30. This is assuming the airline does not go under. That will give you ten years to upgrade to captain. At age 40 you will be a low end captain. By age 50 you will be a high seniority captain at max pay or near max pay. Then you have 10-15 years to have max pay with a great schedule.
In a perfect world maybe...
I was hired at UAl at age 29 was a captain by age 40 and am now a very junior F/O on the 757/767. None of this stuff is scripted.