Why, in your shooting, is second-curtain the most usual/interesting? I think of this mode as required for subjects moving in the dark where ambient light needs to show movement of flash-lit subject more as expected. Hmm, "expected" -- I mean show the time relationship implied by the shot more as expected.
Hard to figure out the right words but I hope you know what I mean... why shoot so often in "second curtain"? Long exposures -- often -- when you have flash(es) set up?
This makes me want to experiment at the next party!