This is super helpful, thanks everyone for chiming in!
One more hypothetical - could I do this:
Ticket 1:
Monday: SFO-DEN .... Following Monday DEN-LAX, Tuesday LAX SFO.
Ticket 2:
Saturday: EGE-ORD-EGE
In other words, can I buy a separate ticket for that one day turnaround to Chicago and back in the middle of another round trip ticket? I think I've always thought that wasn't allowed...
(of course, the other thing is that it looks like AA no longer has a Saturday EGE-ORD flight, so it's probably a moot point)