Since this thread started, I had to re-tighten my Nukeproof Horizon composites on my BMX a couple more times, even with generous loctite, eventually I cleaned the loctite off and glued the end caps in with freaking epoxy. Take that pedals.
The composite Nukeproof Electrons I have on my around-town bike, the endcaps do stay in, but the crappy rubber seals on the spindle side come loose instead and ride up the spindle, doing a great job of keeping the spindle spotlessly clean but a terrible job at keeping stuff out of the pedal.
I mean I don't doubt most people have good runs with them, but there just seems to be better options. Vaults and other DNN pedals obviously but I think I will look at OneUps for the next composite pedals I buy.