Originally Posted by
docbert
As has already been said, changing the ticket today will (probably) re-price the entire ticket as if you'd bought it today. If you wait until after you've flown the outbound, it will (probably) re-price based on the prices when you originally booked the ticket, but it will be based on the availability at the time you're making the change which could well be lower than today. ie, it's possible it's better to change today, but also possible it's better to wait and do it after the first leg - there's no way to know which will be better.
Actually, I think the standard UA fare template allows for changing the return at any time using historical fares. I think they finally decided it was silly to give people who waited longer more options. The rest of your analysis is spot on, including the inability to delegate an R fare to B on the long-haul flight.
Originally Posted by
docbert
The reason I've put '(probably)' there is that it technically depends on the ticket rules, and the comments you've made about no refund when changing to lower fares makes me think that you're not on a normal/publicly available ticket/fare, as generally you would get a refund in a situation like this, at least for tickets starting in the US.
Most UA fares actually have this same verbiage about no residual when changing to a lower fare. They then override that provision to give Future Flight Credit
when UA is making the change themselves. Travel agents are still required to follow the fare rules. It’s… a sketchy business practice at best. If you care to give UA the benefit of the doubt, it’s probably influenced by the fact that the new type of FFC is closer to an internal ledger than the older change system. I don’t think UA has put systems in place to allow TAs to generate FFCs.