Again I was thinking 12-15-ish years, so the guy actually makes some CA money for a few years.

Retirements are pretty negligible on the AS side. I don't know for sure but have heard HA is similar.

The "Hopefully" part comes into play in the event that some WBs go away (AZ), and there is NB fleet consolidation.

So yes there is a risk that upgrades could drag out even longer than today. "Hopefully" not but it is possible with consolidation/stagnation.

If the guy wants to upgrade no later than 64 1/2, so he can have scrambled eggs and four stripes in his retirement photos, yeah that should be a safe enough assumption.

Anyway that's the worst case. And I mean realistic worst case because it could happen if DL gets real aggressive in SEA and SWA in CA and HI (not trying to factor fringe cases like asteroid impact, pandemic, nuclear war, etc).

There are also many better cases.... growth, early retirements, etc.