I like the idea of there being a second five-year mission, even if it isn't "canon." I also envision them changing their outfits quickly to the TWOK-on uniforms about a year into their mission, as I can't bear the thought of our heroes zipping around the galaxy in earth-tone pajamas with footies for a full five years! Can you imagine the laughter of Klingons when they'd see those outfits? Esp. the footies?
You might be suprised. The TNG Klingons would respect them. "How strong and powerful and without fear these Federation warriors must be to enter into pitched battle in their jim jams."