Also consider the maxim that "past performance is no guarantee of future results." Translation- Just because someone hired in 2014 upgraded to Captain in 5-7 years is no guarantee that a 2018 new hire will enjoy an identical upgrade time. Indeed, sometimes one year has made a difference between upgrading in 5 years, versus 10 or more years.

As others have pointed out, quality of life is an important consideration. It isn't too difficult to visualize four years making a difference between being able to hold a desirable domicile or not. Would you rather spend a 10 year window being a junior narrowbody crewmember in a tough commute domicile, or spend it as a senior widebody crewmember living in your choice domicile ?