Capo off when not playing?

I'm working on learning a song right now that requires the capo on 1, so I've needed the capo whenever I pick up the instrument lately.  Is there harm in leaving the capo on between sessions, or should it be taken off when not in use?  Part of me thinks the strings should be unfettered when the instrument is "resting."  Part of me thinks I'm overthinking.  Which part of me is right?  :)