Captaincy or upgrade is decided by seniority in legacy airlines. Doesn't matter if you start as seatwarmer without any required manual handling skills on a longhaul jet or as fully qualified pilot on a shorthaul aircraft. Expect usually around 12 to 16 years in big airlines, except in times of rapid growth where it can be as short as 5 years. However airlines which grow that fast and need many longhaul captains require usually a lot of prior experience in jets which translates roughly into the same timeframe.