For others, you don't know.
Sometimes that's true, but with many programs they give you notice of changes in time to cash out if nothing else. For example, when Sears dropped their optimal cash-out rate, they sent a mailer.
And in fact BA gave almost a year's notice of changes to redemption rates, plenty of time to (a) book tickets, and (b) decide if we wanted to continue collecting with them.
=aw