We've just 6-starred Behind the Door and now need to AFK for 14 minutes with a load of left-over crests.
Please consider adding a trader to every Rushmore challenge so that we can hand in excess crests and excess time at the end of the challenge!
Or even better a "Finish" button when you've completed every star objective that will turn your extra time and extra crests into extra rewards or xp.
This has bugged me for a long time now, but since the challenges got hit with the xp-nerf-bat while ago, this would at least give us something back.
What to do with the remaining 12 minutes .... farming portraits .... whoop-de-doo.