Maybe there is an internal limit on how many can be displayed. Since they are never saved, a coder may have thought you don't need them forever.
Well, I've only got 4 of them, and they've been consistent for years. while their disappearing act is relatively new.
Hmmm... I wonder if this is similar to FTM's password info requiring renewal every month?
I'm going to keep track of timing from now on.
Update: I thought I started a thread about this same topic sometime in the past, and I searched to see when, but I've been unable to locate it if it actually exists.