Trial character should be available for however long the trial tour lasts

I suggest the trial character should last as long as the trial tour lasts.

Last night I looked at the time left in the Vader time tour and there were 17 hours left. So I figured I would finish it off in the morning. Now there are 7 hours left in the Vader time trial tour but the Vader trial character is no longer in my roster to use. Why would the character disappear before the trial tour that requires that character is over?