Only one thing is guaranteed - retirements. Age 65 delayed the process but the elephant is coming.

If you assume a constant size, which actually means under-performing vs. the competition in the years ahead, first upgrades should be under 10 yrs. We havn't seen that for 20+ yrs so trying to compare the future using the past as a baseline is pointless.

Junior Captain is about 60% at AA. That's under 10 yrs on retirements alone. Early outs, expansion, would increase the odds of it happening.